Internet Sharing not working after carrier change from Verizon to T-Mobile

[Jacob F]

This phone is stubbornly trying to be Verizon. I've added Tmo APN info. I get sweet fast LTE from Tmo. But the instant I try the Internet Sharing switch, I get the following box:
"Connection Not Shared"

"To enable tethering on this device, go to Cell Phones, Smartphones & the Largest 4G LTE Network – Verizon Wireless or dial *611"

Please help me out here. I am allowed 5GB of tethering from TMO. I just wanna use it.