Xfinity Support / NEED HELP

I'm having a HUGE issue because XFINITY is charging me on every 25th of every month since April for a mobile service I don’t have anymore. I cancelled it on March 30th and have already contacted you twice by phone. During the first call, they said they would refund the money that was being charged because the service was already cancelled. And today, July27th, they told me that the cancellation should have already been processed, but it still hasn’t been cancelled, and I haven’t received any solution, and they keep debiting the charge on the 25th. I'm not in the US to go AGAIN to an office.