I upgraded to the Mate Pro 10 in hopes of better dual sim function as it says it is 4G on BOTH sims...but in fact it

By far one of the best smartphones actually, fast, dual sim, great camera...

we have tried multiple times ourselves, both sim 1 and sim 2 slot, the phone lines and 4G/LTE data DO WORK perfectly fine on T-Mobile network if you first turn the phone on OR turn the sim cards off and on in the sim cards manager OR restart phone