Hello,
I assume, that by saying "Two SIM cards", you're talking about RUT9 series routers.
If that is the case, then, when it comes to bands compatibility, global RUT9 version (RUT950 V*****) is compatible with LTE frequency band, used by both Verizon and AT&T operators,
therefore, global version RUT9 routers should work with these operators.
But please note, frequency bands compatibility is not the only one thing, that should come into consideration.
In order for devices to work in AT&T or Verizon network, without being blocked by operators, devices must have FCC and Verizon or AT&T approvals.
As its currently stands, these certificates/approvals are limited to RUT9 series Verizon and AT&T versions: (RUT950 K***** North America (Verizon)) (RUT950 J***** North America (AT&T, Bell, T-Mobile))
More information about FCC and operators approvals could be found in Teltonika wiki:
https://wiki.teltonika.lt/view/RUT950_Certification_%26_Approvals
https://wiki.teltonika.lt/view/RUT955_Certification_%26_Approvals
