If you're using either Straight Talk, or Tracfone with their Verizon SIM, I would avoid the Unlocked Pixel 7 & 7 Pro for right now. I'm not sure if it's the phones themselves, or an issue with the carrier, or a combination of both, but it seems they're not compatible. I got my 7 Pro on Wednesday and tried using my ST Verizon SIM and it wouldn't work. I'm coming from a Oneplus 9 Pro and the SIM works just fine.
I say it could be an issue with either the phone, or with ST/TF because when I contacted Google Support to initiate an exchange, the only phone they would let me order with my RMA was the Google Fi version. I contacted support again about not being able to order the Unlocked version. I sent them a screenshot of my order email and a picture of the phones box with the SKU, all of which pointed to the phone being the Unlocked version. They agreed and I'm now waiting for them to resolve the issue of me not being able to buy the Unlocked version through my RMA request. So maybe there could be an issue on Googles end with the Unlocked version of the pixel 7/7 Pro.
I also say it could be an issue with ST/TF, becasue Verizon has recently bought Tracfone and all of their subsidiaries, Straight Talk being one of them. Because of this, I'm not sure if they've basically merged the services to the point where you would need the Verizon version of the phone in order for it to work. This is just speculation on my part though. I did contact Straight Talk support first, where they checked my IMEI/ICCID numbers, which matched what they were seeing on their end. They also ran me through the usual troubleshooting list, with nothing fixing the issue.
Here's a link to a couple threads with people having the same issue. The first one is one I posted the other day:
If anyone is actually using a Straight Talk/Tracfone Verizon SIM in their P7/P7 Pro, please, leave a comment and let me know how you got it to work..