As I have been active recently on the Community forums, a common and very frustrating error that is being reported by new customers is that after attempting to pay with their credit card, the system gives and error, leaving them in a limbo.
I would like to suggest that Public mobile dedicate one person in the back office to address this issue until problem is fixed.
The employee should track all new activations, and as soon as this error occurs, public mobile can message the affected customer to simply acknowledge that they have a temporary technical difficulty which they are working hard to fix and an employee will activate the account and send a welcome message soon (hopefully within hours, depending on the volume).
This would put the new customer at ease.