aple watch 50% off deal

I spoke with agent to switch my phone plan and he offered me free Apple Watch deal. After I agreed, he told me that it was 50% off. I was indecisive but since the value of Apple Watch was about $250 online, I agreed to purchase it and add $5 monthly charge for Apple Watch. I confirmed with him 3 times that it will be adjusted in the invoice. However, after 6 months, I'm still charged full price. I called t mobile about this issue two times and agent says they will fix it. I don't know if it was scam or what's going on here.