The Defender Wireless trail cameras come in two versions; AT&T and Verizon. These cameras work independently from any existing cellular service you may have, in fact you don't even need to have existing cellular service. The cameras functions, controls and billing occur via the Strike Force Wireless website/app: strikeforcewireless.com
In deciding which version will best suit your needs the coverage of each carrier in the area the camera is going to be placed should be considered. Coverage maps can be found on the carriers websites.
Currently both models work in the US and the AT&T model in Canada.