I've seen mixed things online about supported networks for the phone, with a PDF from AT&T's website that the ROG Phone 7 (both ultimate and nonultimate) were accepted. However when I went to get it activated they told me it was NOT supported once they searched my IMEI (that feature was not working on their website at the time but they can check in store).
So far I've had success with both Mint and T-Mobile, but don't assume that just because it is GSM that it works with AT&T. It's disappointing/confusing to me that that's not the case, but I guess I should have researched more into it.
Now it could be that some specific SKU of the ROG Phone 7-nonUltimate works, but I can't find any information online to back up that claim.
If someone has an ROG Phone 7 that is on AT&T I'd like to hear your experience.
I have Rog 7 non-ultimate tencent version.
after I inserted my att sim card, they sent me a text telling me that the phone is not supported. But actually everything is working fine. Data, text and calls. Even VOLTE is working.