I have a 32G Verizon iPad mini retina and put in the Tmobile SIM. Works fine, it was the nano phone SIM not the mobile data SIM. Not sure if there is a difference between the two. Tmobile created a phone number for the iPad mini retina on that SIM. What would happen if I used another nano SIM in the same iPad? Is the IMEI already tied up with the first SIM?