Endless broken promisses on commercial account to win me from AT&T recently

Recently we had a commercial account with AT&T and a local store opened up for T-Mobile and they came by and offered to win my business. The offer was pretty straightforward. They offered to pay off phones and give a credit towards service in the form of cards, they were also supposed to put insurance on the new phones, which we said we would pay for.

Theoretically it was cut and dry.  Then I found out they expected me to pay of my old phones and they would pay me back.  So I did that. 

Here I am 6 months later and I have gotten only half of the credit and recently was told it was because they paid of the phones.  They didn’t, but they literally checked a box that said that they did and unchecking that box is apparently a very long process.

Also, recently one of the phones was damaged and I submitted for insurance and they rejected it saying it wasn't insured. 

I do have a specific person I'm talking to at T-Mobile but he is genuinely doing his best. He checked right after, confirming it was insured and is trying to get them to fix it.  

He keeps getting told things by T-Mobile that a incorrect and then he keeps having to go to bat for me and then keeps getting told things again that are supposedly true but turn out to be false and so it is a weird kind of situation because my representative has shown me the communications and proven that he is being told things that are not true and that he has to keep trying to get the promises made actually fulfilled.

And here is the crazy part.  I do not think any of this is intentional.  I think the T-mobiles internal machine is such a mess that nobody know HOW to make something happen the way someone promises because there are so many hands that touch any one action and it only take ONE OF THEM to mess things up.

So now I have a damaged phone that I have to decide whether to just pay $400 to fix the screen or wait to see if he can get them to approve the insurance claim not to mention all of the massive delays on getting the credit that was promised.

If anyone has any secrets to cutting through this mess other than a lawsuit in small claims court (which I am likely to file next month if this doesn’t get fixed) I would appreciate the advice.