We had the post office cards, also changed to Jaja. There was no balance on them but my wife was unable to activate her new card.
The helpline, when you eventually got to talk to someone in a land far away, was crap. Totally disinterested bod who was very hard to understand.
The app didn't work very well. So we binned them. A detailed complaint letter was sent but only a standard confirmation of closure eventually arrived.
Funny old thing, look on the PO website now and the credit cards offered are run by Capital one!
The old cards were run by Bank of Ireland, customer service was in Ireland. They were really helpful on one occasion we called them.
We used the PO cards as there were no charges to use abroad. Halifax and Santander offered the same so no problem changing.