I cancelled my service

I am still getting bills.  I have returned the equipment on JUly 29.  I have talked to two different people who assured me everything was cancelled and I should get a refund in the mail.  I only keep getting bills saying I am late paying.  Now I can't get an appointment or talk to a live person.  This is the worst customer service.  I did everything I was supposed to.   Now how do I get the bills to stop?