In contract phones deals one has to maintain contract with the service providers for the time period up to 12 to 18 months
. While the time period is running one cannot change their network provider. But as soon as the time period gets over he/she can switch to some other network if he/she wishes to do so.Different handsets like Samsung tocco lite, blackberry bold 900, HTC desire HD, Motorola milestone 2, Sony Ericsson vivaz, Nokia E7, Apple I-phone, LG optimus one and many more amazing handsets are offering contract phones which is given by the network providers.