Why is my phone cutting in and out if not the provider

[AC Question]

It's not my service,I maid sure of that,it says it's dialing after someone answers,cuts in and out even on speakerphone then it drops my calls,I know it's not my service my brother has same phone aND service

 

[B. Diddy]

Welcome to Android Central! Which phone? Maybe there's a problem with the phone's antenna. Does it also happen in Safe Mode?