WHO CAN I REPORT ISSUES THAT TMOBILE CANNOT CORRECT

I have been billed incorreclly, been issued a refurbished phone that does not work properly after my 2 month old new phone went dead!  Then charged a $20 fee to get the refurbished one and was not told that I would incur this fee.  I have called tmobile and they drop the calls without being helped. There are also other issues that they just are ignoring and think they they provided me with service.