Why is Xfinity Mobile trying to steal my money?

While I lived at my old address, I had an account through Xfinity for internet and two phone lines (the account phone number was [Edited: "Personal Information"]). I cancelled the account early this year with the following timeline and problems.

January 30th - I went into the store and canceled my service entirely (internet and both phone lines) to join another account with Xfinity. While it took a few days to get my phone connected on the new account, I was immediately recorded as being part of that new account and paying for that account.

April 27th - I called Xfinity to find out why I was still being billed for the old account I cancelled in January. I was told to go into the store to get my money back. They also confirmed that my account was cancelled that day on 04/27/2025.

April 28th - I went in person to the store. They said the account was not cancelled as I was told it was, but they said they canceled it in the store that day (04/28/2025). They did note that there was a record in their system from the 30th of January where I asked for my internet and phone lines to be cancelled. They said they didn't know why the account wasn't cancelled. I was then told they normally would have put the money directly back into my account where it was taken from, but that card had been lost and replaced. Instead, they asked for my new address to send a check to me with the amount I had been billed since I first cancelled the account in January. I called Xfinity Mobile again that night to confirm. They said the account was canceled, and the amount would in fact be refunded to me. I never received this check.

August 30 - This past weekend, I received a notice on my credit that it would be taking a major hit soon as someone would be sending collections after me. I checked my credit and discovered the collections was from Xfinity Mobile to the amount of $203 through "Credence Resource Mana". It was reported on 8/27/2025 as being "Seriously past due date / assigned to attorney, collection, or credit grantor's internal collection department".

Please tell whoever needs to hear it at Xfinity Mobile: It is unacceptable that an error by Xfinity Mobile would damage my credit and that they would expect me to pay for an account that I canceled in January. Stop trying to steal my money when it is in fact you who still owes me money. Rescind this collection that will damage my credit.