With the major providers, you will need to have a device from that provider. You don't have to buy a new device, per se, but you wouldn't be able to start up service unless you had a device from that provider. So, if you purchased an unlocked GSM device on-line and then went to T-Mobile, for example, and provided them with the IMEI number of that device, they would tell you that the device was not a T-Mobile device and that you would not be able to start up service without a T-Mobile device.
If, however, you started up service with T-Mobile and got a phone at little or no charge and then purchased an unlocked GSM device on-line, you could take the SIM card from your T-Mobile phone and put it into the new device and it would work. A couple of things to keep in mind. The major carriers all test the devices they sell extensively and only sell devices that meet very specific criteria.
If you were to use a device that was not supported by the carrier, you may have issues, such as dropped calls, etc. When you purchase your device through the carriers, with your service, the device is under warranty (typically 12 months) with the provider. You are also guaranteed that the device has been tested on the specific network, etc. So, since it appears that you already have cell service.if it is GSM service (i.
e., T-Mobile or Cingular) and you purchased a GSM phone on line, all you would have to do is put your SIM card in the device. If you have CDMA, i.
e., Verizon or Sprint, you are going to have a much harder time because CDMA does not use SIM cards - your wireless number is associated with the ESN number of the device. I believe you would have a hard time getting them to put your non-carrier phone ESN into the system.
Most providers will allow you to upgrade your phone every 24 months and at that time, you can take advantage of the same types of discounts that new customers get on devices. This all depends. It is common practice in the UK for mobile network to lock handsets to their network, preventing use on any other network. If verizon have done this you would need to have the handset unlocked befor you use it on Cellular's network.
Once unlocked, or if it is not you should have no trouble!.
Victor Epand is an expert agent for BuyCellularPhones.info, a huge cellphone superstore featuring great prices and rebates on cellphones including Motorola, Samsung, Nokia, Audiovox, LG, RIM Blackberry, Sanyo, Sony Ericsson, and others.