INCORRECT CHARGES

I am acct manager for my disabled brother. 9/6/26 he moved 5 miles away, wanted to transfer his exact service. Instead new acct. opened my name at his address. That acct then closed and new acct opened in his name, now has a $600 bill. His payments auto debit, whatever was billed was withdrawn from my acct, never missed a payment, have all of my bank statements. Sept bill not withdrawn until Oct 1, not our fault, still pd for Sept., just paid $200 for Oct .  If we have never missed a payment since at least Jan 1, 2026 how can our bill possibly be that high? Cust. svc keeps telling me a $231 balance due at prior address for Aug. If Aug was paid, how can there be a balance due, with no change in service requested?Exact service to new address is all we wanted, Never missed a payment, bill is enormous. Customer service very unhelpful, even started hanging up on me. I have plenty of documentation available. How is this possible? At one point having 3 accounts for one address? Xfinity store told me they cannot help me. Again, every month payment withdrawn by Comcast in the amount of the bill. This is making me literally crazy - it simply cannot be correct! If bill auto paid every single month, and exact service transferred, how can there be a $600 bill and they are not backing down! We have had Xfin for everything for 15 years but i have no problem leaving - i will not pay this bill. help!!!