How to escalate a complaint

  I received a text from T-mobile.  They said I could buy 2 I phones get $700 off one, and receive a free line.   I called T-mobile, they checked my account and said yes you definitely qualify. I then went into a chat session and asked again and they again said yes I qualify(I have the print out)  So I went into the Store, I again, in front of 2 other live witnesses , asked them to check and see that this promotion was available to my plan before purchasing the 2 I phones. Again, they called spoke to another manager and yes they said all was good.   So we purchased the I phones, received the new sim card for the new line and everything was fine.  Until I got my bill, T-mobile was charging me $10 for the new line plus the other fees( fees which I already knew I would have to pay. I am not opposing those fees.  )   

So I chatted with T-Mobile, the rep agreed (I have it from the chat printout) I should not be charged, he took the fee off and said that all was good. 

Low and behold next month the $10 charge was again on my bill. I again called up another rep Christopher.  He said yes I see the problem.  He again removed the $10 charge and said that it was taken care of……Nope, next month the same thing I talked to another girl Crystal, she again agreed that I had did everything correct and there was just a delay in the billing. She took the $10 fee off and  she begged me and I mean begged me to say that the problem was solved.  I refused and told her until I see that the charge is not on my monthly statement I would not say the problem was resolved. She reluctantly said ok. 

Guess what the next month the $10 charge was their again!!!!! So I went into the T-Mobile store and at first they said they would take care of it then they started saying no this was only for some other promotion???? What??? I confirmed several times, printed from chats and if I wasn't eligible why would they all have said I was and agreed to take off the charges??? 

So the manager at the store, Said he agreed and would look into it.  I sent him all the chats, the copy of the texts, everything.  This guy tells me later that the girl that he was working with to get it resolved was let go and there was nothing he could do??? WHAT?  Was there only one individual in the company that could take care of this????

To me this is clearly a bait and switch scheme that T-Mobile is trying to pull off. Much like their "oh if we merge with Sprint we will create jobs"  but now we know that T-Mobile is laying off 5000 employees.

So I need to know how to escalate this and if anyone else out there experienced something similar so I can present it to the attorney general and the fcc.