Cheapest plans does not always translate to better service.  If you don't really have lots of need to interact with your provider except pay every month, probably cheap is the way to go.  But if you need to call them and complain and request for credit for some call, then forget the Sprint cheap plans.

AT&T is not great either on the customer service side from my experience.  They stuck me with an overseas call I never made and its a no win situation. I know because it was back billed from the prior month and don't make international calls.  Thier tech service is below par, not knowledgeable.  They go through steps like in a service manual.

Verizon has great service but price is high.   If you afford them, why not.  Tech support is good if you can get to their 2nd tier support.    They will charge you for anything they consider violation of their usage rules eg. data usage.

TMo is almost gone if AT&T gets its way.