Max transit super slow with new Sims from SAME provider

Hello there!
My friends max-tst-duo-ltea-w-t has been crawling since he consolidated his 4 t mobile sim plan down to a 2 sim. He originally assumed it had 4 slots so it needed 4 sim cards, not understanding only 2 ports work at the same time. As such t mobile had split his data cap between 4 instead of 2 and he ended up getting throttled if he didn’t swap the sim cards out.
After no less then 20 hours on hold and dozens of visits to the store the t mobile rep just recreated the plan they had before with 2 cards and told them to cancel the existing 4 sim plan.
The problem is that the new sim cards can’t seem to provide more then 1mbps at ANY time. The old cards, with the same exact carrier and plan never went under 60+ with both sims active.
Does anyone have any idea what could be happening?

As you suspect, it sounds like the SIMs are being throttled to me. No obvious technical / hardware reason at all. Signal strength is great

You’ll need to go and kick down some doors until someone finds someone who can ‘refresh’ the plan on the SIMs.

What plan were the SIMs before and what plan are they now? Exact plan name/code? Something must’ve changed or is being throttled/deprioritized. Confused why if there were four data lines, why not simply cancel two? Why re-create anything?