dallopharsi, question ni ali dallo-dallo pharsi jastai bhayo ni.. ....no offense plz
it all depends on where you live and what kind of service do u want and how much you can pay....
t-mobile is cheap, but have limited signal power like better in the big city and not so good in the certain parts of the city and also does not have good data plan
att is good, signal and data is also good i guess
verizon is the best if i believe in all scenario but monthly plan is expensive as compared with others..... 
so depending on how much you can offer or where u live matters when u choose the cell phone carrier.