email hacking

I have experienced many (at least 15) instances where my xfinity password that I had used successfully can no longer be recognized by xfinity.  I have changed the password successfully, but have had the same problem recur.  I contacted Xfinity and on two separate occasions I was promised a phone call by the Xfinity Security group.  In each case, they did not provide the promised phone call.  I am very concerned and do not know what to do.  Any advice (particularly to get Xfinity Customer service to respond professionally) would be gratefully appreciated.