URGENT: CANCEL MY SERVICE. I’m traveling for a year internationally and can’t call

Hi,

I need to urgently cancel my Xfinity service. I’ve tried canceling before leaving but with the sudden departure was not able to do it. The online assistant is not helpful and my friend went to return the box and they told him he couldn’t unless I deactivated it. There is no option to do this on the box. What option can there be?