I need to cancel a Wifi plan I am no longer using while I am abroad

Hi all,

So I purchased a router and became a Xfinity customer a little over a year ago. I used the services for a month, then transferred ownership of the account to a roommate after I moved out of the premises on rather hostile terms. This roommate has been handling the payments and the management of the wifi for the past year, but as of last month, has stopped making payments, and now the bill keeps going up. After several painful conversations with Xfinity Assistant, the live agent I was connected to told me I need to provide verbal confirmation with a callback. Trouble is, I am currently abroad (Turkey), my U.S. phone line (Verizon) is out of commission, and I can only take calls on my Turkish number. I wish to cancel my services and free myself of any obligation to Xfinity going forward. I scheduled a callback but have reason to believe they will not reach me on my Turkish number. How can I remedy this situation?