Received "loyalty credit" - then taken away and forced to repay over 12 months. Need help....

Really weird situation here, back in August my bill suddenly reflected a $311 "loyalty credit" with no mention of why we got it. I tried to pay my monthly bill, but it was returned because of the credit. Same thing happened the next month, and partially into the third month. I was happy with the credit, and thought it was a credit because we didn't take them to on their free mobile line plan.

Then, out of the blue the credit vanished from our bill and we were setup on a 12 month payment plan to repay the three months we were unable to pay ourselves. Now, none of this was with our knowledge. We didn't approve this payment plan, nor did we ever receive an email explaining what the hell happened.

Has anyone else experienced this? We are loyal customers since 2000 in the AT&T days and consider ourselves good customers for Xfinity with our 2gig plan, always switching to the best they have to offer, but this is the first time we're considering an alternative provider for our Internet needs. I'm primarily dismayed that they can set up a payment plan without notifying us, and hand out credits without disclosing why they are applied.

Anyone else seen this phantom credit and payment plan? Hope to hear from you (and someone from Xfinity).