Bill STILL not fixed after 5 tries

My bill has been 5 different prices in as many months. I’ve been told 5 times now that they will fix my bill… they even comped my bill a few times to make it better but the next month , it’s still wrong. I’ve also been charged for multiple pieces of unreturned equipment that I sent back thru the mail. If I don’t get his fixed today I’m switching to AT&T. Please help me.