Cancel service

I have been trying to cancel my xfinity internet since last month, but every time I call customer service, they lie to me about cancelling it. On my third call, they even sent me an email saying, "We received your cancellation request and we're on it" on July 9, but nothing's changed. 

Can someone please help me cancel my internet service, I'm moving to a different country soon and need to cancel it asap.