Unlocked Sprint LS980 G2 SLOW data speeds on Tmobile service topic

Good Morning and thanks in advance. I have a Sprint LG LS980 that I unlocked and i'm using it on Tmobile prepaid 4G () plan. The data speeds however are extremely slow. Like I barely get over 3 Mbps Up or Down. I'm no stranger to flashing, adb and i've read the FAQs and whatnot on the G2 but cannot find a specific issue of data being slow. Is this a network issue or is there a radio I need to flash, or setting I need to change to make this work correctly. It doesn't appear that I'm getting 4g LTE although I'm not entirely sure that the G2 has the frequency for it. I have troubleshooted this issue with tmobile in store folks as well as customer technical support and their answer in the end is always "It's a sprint phone so it's not designed to work on tmobile" Please point me in the right direction. Thanks.