That plan is a great deal if you travel to the US with some frequency. This is what drew me to PM in the first place, was sick of gouging by other providers and living close to the border, it became a no-brainer for me.
In the PM app, choose "Manage Subscription" and then "Change Subscription", you should be able to select any of the available subscriptions. I just switched my subscription to another without any issues this way. I picked to do it on renewal, not sur...