It does pay to go up the chain of command. I have been able to get many credits that the customer service people told me were "not possible". You have to be persistent & keep trying until you get what you want.
All you need is a history of their screw ups, which are all over their computers with us.
It's like a marriage counselor I heard on the radio years ago said if you are married ladies, don't divorce you husband and get another one, one's as bad as another...Cell companies are the same.
We have 6 phones altogether and have to have them working to do business efficiently.