trying to find a way to cancel service when I'm out of country

Hi, I'm trying to cancel my internet service because I’ve moved out of my previous apartment and am currently out of the country.

When I looked into the cancellation process, I was asked to provide a callback number. However, since I'm overseas, I'm unable to receive a callback. I would appreciate it if you could provide me a way to cancel the service immediately before my auto-payment. (I also couldn't find a way to cancel my auto-payment as it shows errors on the website when I try to.)