T mobile Offer not honored

In December, I was made an offer to switch mobile operators. They offered to refund me the amount I paid for my phones with that operator. After that, they sent me the SIM cards and the phones, but it wasn't until January when they activated them. Additionally, I took an iPad without confirming that I would keep it.

As of today, they have NOT refunded me the money. The agent handling my case says that there was an "error" when activating the lines and they cannot refund me. In addition to that, |TMobile charged me from December to January WITHOUT ACTIVATING the lines, and they have also NOT provided instructions for returning the iPad. And keep charging it into my bill.

Nobody is taking responsibility for my case. My advisor is not responding to my calls, and call me on each 15 days, and the person who activated the lines late is washing their hands of it, as well.

My switch to T-Mobile has been a nightmare, and it seems like they don't want to honor an offer they made to me on December. The conditions regarding the erroneous activation are the responsibility of T-Mobile and its agents, not mine. I have everything in writing.

I´m paying more that offered, they can not honored the offer made, and can not received the IPAD back (new, on this box) to keep charging my bill for it?. How can help me on that?