carrier change on pre-owned lte gx440?

I am considering purchase of a pre-owned gx440, I have only recently begun using these products.

I need to use Verizon, and the vendor of the pre-owned unit tells me the gx440 in question is “at&t/verizon” since they’re both LTE networks. Is it simply a matter of which carrier’s SIM you put in and activate? I am thinking I should also I expect to install the 4.3.6 firmware package for Verizon, if I find it a) has an old firmware or b) if it is programmed with an at&t specific firmware. Either way, I would plan to follow the firmware upgrade path indicated in “Application Note: Updating from Older Version of ALEOS".

Any insight or recommendations? Thanks.

The unit can’t be AT&T/Verizon as they are separate models with a different module inside. An AT&T model will not work properly on a Verizon network and same goes for the Verizon modem on the AT&T network. It is better to make sure which model you are purchasing.