Wireless Joint

I need a plan that will work in Mexico, so I may start with the Cricket 100gb plan and then switch to ATT (unless I missed something and ATT prepaid works in Mexico)

Note: This is a completely hypothetical question that I'm curious about to strictly understand how modems/routers work:

If someone were to change the IMEI number of their Nighthawk MR1100 to an smartphone IMEI and put a cellphone plan SIM card in the nighthawk, would the carrier count the data as ...

Sorry if this is a repeat question, but I've read so many conflicting posts about this question, so I'm hoping to get a definitive answer....

I currently have an ATT unlimited elite plan for my cell phone, but I was thinking about adding a line to get a sim to use in my pepwave transit cat-18. I ...