T mobile Upgrade

From London, 1 post

Hello all. Maybe you can help me with a dilema I have. I am due to Upgrade soon but T mobile is only offering me line rental discount or Upgrade but no compromise on both.



If I buy a phone myself from India (much cheaper) then take the line rental discount can I swap the sim card over and use my newly bought beauty?

They once said to me that wasn't allowed but

why should they even have to find out?

Furthermore will it not be better to save on call charges through line rental discount.