Returned phone billing issue

I returned a phone purchased/returned through third party retailer. It was received back 9/2, installment is still on my account. It was within the 14 day period, and I have provided multiple forms of proof to AT&T.

Multiple attempts at resolving through chat, 611, and Loyalty and Retention have been unsuccessful. Last person I spoke with assured me installment would be resolved Wednesday last.

Is there an AT&T employee here who can actually help?