I seem to remember a further complication with iphones and current OS is that the 2G GSM option is no longer selectable. I seem to think it can switch down but sometimes some areas won't work for that. Whereabouts are you? There is no T-Mobile in Alaska so since your phone does not have volte and talk only works on T-Mobile, T-Mobile has nothing for us in Alaska.
You can still text and use data on AT&T but you need T-Mobile and their 2G GSM for talk.
Do you have a Canada US plan with Public Mobile?
Did you purchase an add on to use in the US?
If you have one or the other, you may need to set your phone to T-Mobile. This is how you do it. One is Android and one is iPhone.
Please remove your personal information by clicking on the V in circle and edit or your will get spammed.
PM doesn’t have service in Yuma, AZ unless your have purchased a U.S. Roaming Add-on. Login to your account and make your purchase.
You can use WhatsApp on wifi for free calling and texting.