PNA card change - big saving for them

I’ve always had great service and their loyalty card certainly paid dividends. Until now! I was advised at the till that my old card was no longer valid and that I needed a new one. That was simple enough. BUT then she told me that any funds in the old card would not be carried over to the new card. She was also unable to tell just how much was in the old card”old” card. Poor show PNA done without any prior notice.