For this inquiry of yours, I would like to know what is the Product Code of the RUT240 you bought from Amazon?
Kindly refer to this link:RUT240 Supported Frequency Bands - Teltonika Networks Wiki (teltonika-networks.com)
For AT&T and T-Mobile the Product code is: RUT240 X2XXXX
For Verizon the Product code is: RUT240 X1XXXX
I hope it helps