@revrae - SIM card follows your PM account/plan/phone number...so all good there.
Not a bad idea to perform a Reset of your device's Network Settings on the iphone 7 with the PM SIM card inside.
This also resets Wi-Fi networks and passwords, cellular settings, and VPN and APN settings that you've used before.
To Reset Network Settings, begin by opening the Settings app. Next, tap General -> Transfer or Reset iPhone -> Reset -> Reset Network Settings. and enter your passcode.
Your iPhone will reset network settings and restart itself.
If this is a used iphone 7, check to see if you need to deregister a number on the iphone it may be registered with: https://selfsolve.apple.com/deregister-imessage/
Set up your phone number On your iPhone:
- Go to Settings > Messages and make sure that iMessage is on. You might need to wait a moment for it to activate.
- Tap Send & Receive. If you see “Use your Apple ID for iMessage,” tap it and sign in with the same Apple ID that you use on your Mac, iPad, and iPod touch.
- In the "You can receive iMessages" section, make sure that your phone number and Apple ID are selected.
- Go to Settings > FaceTime and make sure that your phone number and Apple ID are selected in the "You can be reached by FaceTime at" section.
