Disasterous chnmge to their IT system

They have changed their system for awarding points for use of their black credit card. You have to download thier app, but, when you do, it doesn't work on my iPhone. I have been waiting to get my quarterly cashback since May. The voucher used to be emailed to me. I have tried going into a branch and speaking to them on the phone, but neither could make it work. It's a total disaster.