Third line charged for number transfer

Hola,

I went to the T-Mobile store in January to buy a two line Magenta Max contract. My wife wanted a new number and I wanted to transfer my number from GoogleFI, so the sales rep created a temporary third line during the process that we needed to take over my number. The idea was to make sure that I won't cancel my number with GoogleFI too early and run into issues (I used the number for multiple 2FAs).

For some reason, I was billed this third line in my first month even though I have never used it. I was also not informed by the sales rep that this will incur any costs. I assume he didn't know either but he was very quick and knowledgeable. I then asked T-Mobile support chat to give me a refund two times over the course of a month and was promised that I will get a discount within the next 2-3 future bills. Instead of the refund the chat removed my employee discount for some reason and I had to call the hotline to get it back on (this is solved by now). The refund for the third line first month has not happened so far. When will I get my refund for this temporary line? Had anyone else similar issues and what is the best way to handle this? Chat support seemed not to be very helpful.