Canceled in Feb, billing continued(and continues)

Let me preface this by saying that I have contacted Xfinity customer service FOUR times already; twice via chat, twice via telephone.

On Feb 2 I contacted chat to cancel my Xfinity service. I was assured it was canceled.

A couple weeks later, I got another "your bill is ready" email. I again contacted chat, they told me to ignore it, it would not be billed and my service was canceled.

A couple weeks later, my bank account was debited for payment of the bill I was told to ignore. I now called Xfinity customer service. This person had no idea that I was supposed to be canceled, and swore they took the steps to cancel it and would be issuing me a refund of $100.xx (yes, they quoted me a specific amount I would be getting back).

A couple weeks later, I AGAIN got a "your bill is ready" email. By this time I had gone in and removed any autopay information from my account, thankfully. I once again called customer support and was assured that I did not need to pay it, my services had been canceled, back dated to Feb 2 (when I originally canceled) and I would be receiving a refund to my method of payment (bank account).

Now, here we are another few weeks later and I just got a paper bill saying I owe an additional $2.56, and I have never received a refund.

So, this is my FIFTH attempt, in 3 different methods, to contact Xfinity and get this resolved. It is ridiculous that this takes so much hassle to perform a very simple transaction. How can I go about getting ahold of someone that will actually do what they say, ensure this service is canceled, and issue me a refund?