Anyone? NO number to check on "Notice of Dispute"? Do I just move straight to Arbitration?

For 26 months we've had unbelievable billing discrepancies, which look like data entry results from an MS-DOS based computer system by people that barely understand the language they are written in. Things that stick out like a sore thumb:

Wireless charges for warrantied equipment AT&T has (with tracking info verified)

Wireless charges for a "free" tablet that I have a receipt showing paid in full (copy sent/verified)

Promises to reimburse the $932 many, many times. (And always "just wait 24 hours, I already see it on my end")

26 months of begging and pleading every month with combined billing to just get it right... 

I don't feel like kind, polite, patient, loyal customers should be treated like garbage. Combined billing nightmares seem to outweigh everything else on this forum. These extremely expensive mistakes deserve to be corrected. It is the right thing to do. If anyone has had ANY luck, PLEASE share your advice. 

Heartbroken with T-mobile, but at least they are kind (and don't hang up polite people for no reason.)

Any phone number to the Dispute Resolution department would be fantastic. An email would even suffice. It is impossible to only have "snail mail".