Xfinity cleared my charges and I have photo proof - now they want to charge me cancellation fees

I was relocated for work and no longer needed service with Xfinity. I told them about this move and the agent I spoke with told me that my account balance was $0 and no early termination fee would apply. I have photo evidence of this chat. Now they are attempting to walk back that statement. The agents are representatives of their company and thus, I shouldn't have to pay this amount.