Poor service, lack of accountability for customer service

I've been having problems with my AT&T home internet.  Both wired and wireless.  

My speeds are inconsistent at best and jump from 16+mbps down to less than 400kbps.  I cannot watch any streaming video without it being interrupted to buffer, in the best case scenario.  Watching movies is painful as the connection cuts out multiple times, every time.  

 I reset my router at least daily.  AT&T last replaced the router about a month ago because apparently my old one went bad.  Although they were never going to tell me that it had gone bad or replace it unless I made a stink with customer service, which I did.  I talked to so many people before finally finding one competent customer service representative who could help me. 

After replacing the router, I think I had about 2 weeks of normal service.  Since then, it's been terrible.   I've been using the chat feature to reach out to AT&T for the last 4 days because my service has been so bad.  I HATE how there is ZERO accountability for their words.  Each rep wants to help and promises me that they'll fix the problem but nothing changes.  I've been told that I'd have a supervisor call me which has happened once out of the probably 8 or 9 times I've been told it would happen.  The one time I did receive a call, the supervisor was rude and essentially useless. 

After  every chat session, I have the transcript emailed to my email.  Sometimes I get the chat sent to me, other times it does not work. 

Does anyone have any advice on how to connect with anyone at AT&T that can actually help me?  Is there a way to hold the representatives accountable for their words?  I'm so tired of explaining my situation over and over again and living this Groundhog's Day cycle of dealing with the same problem and talking to the same ineffective reps over and over.