In India, we use the digital network specified as GSM 900 (Global Systems for Mobile communications). The digital standard, including CDMA, TDMA and GSM platforms, allows for more callers to at the same time, occupy space on each of a service provider's cells, making it the superior choice for highly populated or metropolitan areas. Disadvantages to digital systems are their lack of unified technology and a small, metropolitan-focused calling area.

Ask yourself. Do you want a cellular phone for emergency use? Will you be using your phone/service around town? Travel a lot? Planning a coast-to-coast?
Whether local, National or International you'll want to choose a calling plan that encompasses the physical boundaries of your calling needs. While using your cell phone on an occasional trip away from home may add extra roaming or long-distance fees to your bill. National plans, are more expensive than local plans,but will give you the freedom to call regardless of your geographical location.

Caller ID, three-way calling, voice-mail, numeric paging, call forwarding and Internet access are just some of the great options offered to calling plan subscribers.

Subscriber Identity Module, or a SIM card is the key to European and Asian mobile communications, the digital equivalent of an ID card. All the information about the service you subscribe to, your plan details, your phone number, etc. are stored in this thin, credit card-like unit. It's placed in the handset to activate the phone and your service.
A SIM card contains integrated chips that extend its intelligence and capabilities by leaps and bounds. Apart from being able to store your entire phone directory, this smart card provides access to a whole range of applications such as short message service, mobile banking, and even the mobile Internet. Your phone becomes personalised and user-friendly.
The big advantage from a user's point of view is the great flexibility of SIM cards. When traveling, you don't need to carry your phone, just take the card. Rent a phone from the airport once you arrive, slip the card in the phone and you are again connected to the world, with the same phone number.
Each card has an authentication code, a password or a PIN, specific to your service provider, which ensures that only you are using the card. GSM's encryption technology is fairly advanced and is considered to be one of the most secure technologies in mobile communications.
PIN / PUK
The SIM Card has a security feature called the PIN / PUK- a four-digit number. You can change this number to any four-digit number of your choice using the handset. Once set, three wrong attempts of entering the PIN / PUK can get the SIM card blocked temporarily. It now requires the Master PIN / PUK number to unblock the SIM. Generally ten wrong attempts to enter the PUK number can get the SIM card blocked permanently and it will require a SIM exchange.

The SIM Card can be permanently damaged, if

Caller Line Identification Presentation (CLIP) This feature helps you to identify the caller by displaying the number on the handset. Since you know the caller's identity, you can respond suitably, depending on the importance of the call. You can return the call later in case you are unable to answer immediately. The service is provided free of cost on all bill plans except the Standard Bill Plan, where it is charged about Rs.75/- per month in Mumbai.
Caller Line Identification Restriction (CLIR):
This feature enables you to restrict your cellular number from being displayed on the receiver's cellular phone. It helps you maintain complete confidentiality of your number. The service can be obtained at an additional cost of about Rs.75/- per month in Mumbai.
Call Waiting / Call Hold:
This feature allows you to receive another call when you are already answering or making a call. You get a beep indicating an incoming call. Using the 'SEND' button you can receive the call by placing the first caller on hold. You can switch between these two calls using the same button. You will be charged airtime for both the calls. The service can be obtained at an additional cost of about Rs.75/- per month in Mumbai.
Call Conference:
This feature allows you to speak with five people at the same time from wherever you are. It is just perfect for times when teamwork matters so much to job success. You can have a conference with either cellular or landline phones including STD and ISD calls. All calls will have to be initiated by you. All your calls will be charged the Airtime and DoT charges as applicable. The service can be obtained at no additional cost in Mumbai.
Call Divert:
This feature allows you to divert an incoming call to a landline or to any AT & T cellular. This way you don't miss out on any important incoming calls. Calls can be diverted when you are busy, unavailable or traveling. The call can be diverted to any landline or cellular within the AT&T network area. Calls cannot be diverted to a cellular of another service provider. The service can be obtained at no additional cost in Mumbai.
Call Barring:
This feature allows you to bar incoming and outgoing calls using a four-digit password selected by you. This is a security measure to prevent the possible misuse of your cellular phone. This feature will work only if the Call Divert feature is de-activated. You can selectively bar all incoming calls or all outgoing calls as well as outgoing ISD calls. You cannot selectively bar outgoing STD calls. The service can be obtained at an additional cost of about Rs.75/- per month in Mumbai.
Short Messaging Services (SMS):
The Short Messaging Service allows you to keep in touch with your colleagues, associates, clients who are customers & currently are outside the coverage area at the time of your calling them. Standard messages created by you can be stored in your handset and sent as required. Just pay a Re. 1 for local sms, Rs. 2 for National sms and Rs. 5 for International sms in Mumbai under a post paid plan.
Detailed billing:
A detailed statement of your calls from your cellular phone, the call duration and the applicable charges can be sought. This is the most comprehensive billing statement for a person who values both time and money. The service can be obtained at an additional cost of about Rs.75/- per month in Mumbai.
WAP:
The latest innovation in mobile telephony, it enables the user to browse the Internet on his handset screens however, handsets which are WAP unabled are required for using this service.
Network Circle Coverage (NCC):
This allows subscribers to call a PSTN number in any district headquarters and adjacent area, as defined by DoT, irrespective of distance but within network, at airtime charges plus local DoT access rates only, thereby, saving on DoT inter-city STD charges. Any subscriber who doesn't apply for the NCC feature would be billed for inter-city STD charges (as per DoT rates) and applicable airtime rates for calls made from mobile on PSTN outside the SDCA location of the originating call.
Cellular 2 Cellular (C2C):
Customers opting for C2C would be eligible for the following subsidised airtime rates from cellular to cellular within the service provider's local network. Outgoing cellular to cellular would be charged. Incoming calls from cellular to cellular (within the network of the service provider) is FREE for some users (as may be offered by the service provider) in Mumbai.
Monthly Access:
A monthly charge for the ability to connect to a wireless service provider. This fee is assessed monthly whether the phone is actually used or not.
Off-Peak Period:
Most service providers define the off peak period as nights and weekends. Network service providers tend to offer lower rates during these periods when network demand is low.
Peak Period:
Most service providers define the peak period as weekdays between 9:00am to 9:00pm. Network service providers tend to offer higher rates during this period when there are high levels of communications traffic on the system.
Peak Minute:
Many service providers offer a package of minutes, which can be used only during the peak periods.
Off-peak Minute:
Many service providers offer a package of minutes which can be used only during the off peak periods.
Anytime, Anywhere Minutes:
Many service providers offer a package of minutes, which can be used during both peak and off-peak periods.
Contract:
Many network service providers offer service plans that include a one, two or three year commitment. Carriers often offer discounts on wireless phones if you subscribe to a service plan with a contract.
Rate per Additional Minute:
Many service plans offer a package of minutes per month. Once the subscriber surpasses the allotted minutes in a month, they will be charged a fee for each additional minute of use.
Regional Roaming:
In some cases, there is an additional charge for placing a call outside of the local calling area.
National Roaming:
In some cases, there is an additional charge for placing a call outside of the home state calling area.
Prepaid Cellular:
A system allowing subscribers to pay in advance for wireless service. Prepaid is generally used for credit-impaired customers or those who want to adhere to a budget. But the per/minute calls are also charged at a higher rate.
BILL EXPLANATION
Airtime Charges:
This includes the airtime charges for the current month in minutes and seconds. Remember this also includes the minutes used in Call Divert.
DoT Charges:
This is given in pulses and each pulse is charged at the applicable DoT rate.
Roaming Charges:
The amount of airtime and DoT charges incurred while using National Coverage (Automatic Roaming) facility.
Home Usage Taxes:
A 5% service tax levied on the entire bill amount. It is applicable on everything except deposits and SIM processing charges. In the first bill it is applicable on the SIM activation fee.
Roaming Usage Taxes:
This shows the tax amount on all outgoing calls while roaming. 15% charged on airtime. If it is an outgoing call, 15% on airtime + Local/STD pulse and if, an incoming call, 15% on airtime only.
Itemised Call Detail:
Shows time, destination, duration and total charge for each call made or received. This is further divided into local, STD and ISD call details. Detailed billing is given if opted for by you at charge of Rs. 75.
STD and ISD Call Charges:
This itemises the ISD and STD calls made during the billing period. These will be attached to your bill.

Costs of the mobile service plan Read the fine print.
There are a lot of hidden costs involved like activation fees, contract termination penalty, monthly service charges for particular features etc. Make sure you know all the hidden charges and penalties for any plan you subscribe to. Analyse short-term benefits and overall plan structures to see if they are worthwhile in the long run and suit your calling habits.
How are you charged?
1. You are charged airtime whether you call or receive a call. 2. Many plans round up to the next minute. If your call is 61 seconds, you're charged for two minutes.
Monthly operational charge
In general, the monthly cost for mobile phone service increases based on the amount of airtime you use your phone for. A very low initial payment may be linked to higher monthly charges, while a higher initial price package, may result in lower monthly charges.
So buy your talk plan accordingly, make sure you get full value for your money
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