I've already canceled my service and being charged anyways

Hi, my name is Florencia I've been an Xfinity Mobile user for around a year and a half or more, but last year I left the states (November 21st) and before leaving I arranged with an Xfinity Representative to close my accounts four days after my flight so I could still be connected outside the US. They explained to me that my next bill will arrive with not only the usual charge but also with the roaming package already included, and I received this bill and pay for it on December 16th. I left the states to live some place else and a friend of mine went in person to help deactivate the account and she confirmed that the Xfinity Mobile account was canceled on November 25th. All this being said, yesterday I had a charge on my bank account from Xfinity Mobile under 'miscellaneous'. I'd love to receive an explanation and a reimbursement as there's no reason for me to still pay for anything related to Xfinity services. Thank you.