Bait and Switch

TWC used to have a strangle hold on my neighbor.  However, recently AT&T reps scoured the houses to get people to switch.  He was nice enough and promised more and a better price so I switched.  However, only about half of what he said was true.  But the main problem is that he promised (in writing) a price.  When I got my bill, it was $20 per month more.  When I called AT&T they said they could not do that price...so I told them to cancel my service.  The rep said instead of cancelling let her "elevate the issue for resolution."  I paid them what I agreed to which was short.  So, this month, I get another bill with the wrong monthly rate and the difference from the other"unpaid portion."  Should I just pay the agreed amount again?  How long does resolution take?