May sound silly, but did you just add 1GB of data or did you add US Roaming? I have seen in the past where a customer has thought they added 1GB of data and thought that should give them US roaming. But you need to buy the ten day US roaming package. Here is another issue with US Roaming that public mobile has stated, "US roaming packages can be impacted by the area you are in." This may not be super helpful but gives some insight as to why you could be experiencing issues.
Open a ticket and you may be able to get a refund through customer service.
US Roaming6
10 day packages
Important: Important: As of February 22nd, 2022, United States (U.S.) carriers have started turning down certain 3G/HSPA networks. As a result, customers using U.S. roaming add-ons will be impacted by differences in coverage or service quality (including 9-1-1 calls) when roaming in the U.S. Customers may also experience changes to services such as welcome messages, voicemail notifications, usage notifications for voice, notifications when trying to make an international call, interactive voice responses (IVR), as well as the ability to set up voicemail while in the U.S. This shutdown will not impact your service in Canada."
