There have been a number of cases of people setting up their plan for text and/or data (ie no talk), and then buying LD minutes for the occasional call they want to make. And it makes sense that they think they can do that as the similar (reverse) situation of having a plan with no data but instead using a data add-on for occasional data is valid.
Anyway, yes PM has added a fine print note to the Plans page "Long distance add-ons require a monthly talk feature on the rate plan", which is good, but doesn't go far enough as it is pertty easy to miss.
What PM really should do in addition is add an block that stops people from purchasing LD minutes if they do note have a talk plan.This could take the form of making the option not selectable (greying out) or an error message, etc
(Since PM has no intention of providing the LD service without the talk plan, is it even ethical to sell it under that circumstance...?)