Had trouble with this when I joined PM. I searched through a number of threads (new and old) before I was able to get it to work. Here's what I did.
1. On your iPhone go to www.unlockit.co.nz/unlockit/
2. Click 'Create APN'
3. Change Settings to 'Canada' and 'Public Mobile' then click 'Create APN'
4. If warning box appears click 'Allow'
5. Click 'Install' to complete APN profile.
the APN may be cofirgured automatically but for some iphone users such as myself,
we only have APN settings for "personal hotspot". not even unlockit.co.nz works 😞