Lied to and billed for a phone that I was offered for free

I come to T mobile in Renton to upgrade my service plan from essential to Magenta and add 1 more line for my son kid watch. As an agent advise , i need to pay $150 for 5 line in Magenta plan, i sweared i asked him 3 times and i had confirmed for  $150 monthly payment for that plan. After i received the bill , it cost first month $220 and $170 for monthly after that. I brought the bill to that T mobile store again for asking, and they said it impossible and they can't do $150. I said if you can't do that , so i would like to return everything back to normal and i would like to return the watch too. They said they can switch back but the charge will be higher and they can't take back the watch because only 14 days for return. I really upset and angry , look like i just got scam by a big company.