Can 4/4s antenna be switched to match Tmobile's 4G network?

Tmobile only offers 4G LTE to phones that are originally Tmobile or factory unlocked phones. When asked, they say this is because phones from other carriers don't have the right hardware/antenna to receive the full strength of their signal... so other unlocked gsm phones like at&t only get 3G speed.

My question is, does anyone know which parts would need to be switched in the phone, or (if Tmobile is lying) a way to reprogram the phone to get full access to Tmobile's network? I couldn't find info for this anywhere online...

Thank you! ! ! :)