Yes, you can. If you purchase a U.S. Roaming Add-on (or have a Canada-U.S. plan), you can make calls from the U.S. back to Canada, as well as to numbers within the United States.
VoLTE is Required: Since U.S. carriers (AT&T and T-Mobile) have shut down their 3G networks, your phone must support VoLTE (Voice over LTE) to make voice calls. If your phone is older, you might find that only data and texting work.
The IMEI Check: Visit the Public Mobile VoLTE help page and enter your device's IMEI (dial *#06# to find it). This is the only way to confirm if Public Mobile has "whitelisted" your specific model for VoLTE roaming.
I suggest you check your phone first before purchasing a US addon or using your points to purchase it.
