Wireless Joint

Network-Interfaces-wireless-edit button on 2.4ghz

You can change the WE826 wifi channel:
Then:

Yes, I have Tmobile on WE826-T2's. Just change the apn and you will be fine, also change the TTL to 64 or 65.

I have never done a T-Mobile tablet plan.
Have done several T-Mobile phone sim plans and they are simple to do.
Apn = fast.t-mobile.com
TTL = 64
And that is about it.
Try the tablet plan the same way. Got nothing to loose there.
T-Mobile are pretty relaxed about people abusing their terms of service ...