Hello.
You may not be able to use data in the US with Public Mobile because you likely need to enable data roaming in your phone's settings, ensure you have a Canada-US plan or have purchased a US roaming add-on, and may need to manually select a network like AT&T or T-Mobile.
Also, not all phones work in the US. Please check the VoLTE list and enter your IMEI number at the bottom to make sure your phone is compatible.
https://www.publicmobile.ca/en/get-help/articles/volte
