Pour service

Went to Pick n Pay bought R931.41 worth of groceries which was supposed to be deducted from my Pick n Pay voucher card. It didn't go through because they were offline and I was left embarrassed with no other cash. Was it my fault they were offline or should you ask the shop every time you go shopping are you online? My friend paid the groceries, but when I asked them for assistance at the customer service station they said they can't help me in anyway. I am really disappointed since I've never experienced this in the Northern Suburbs. I love doing my shopping at Pick n Pay but I will not be returning to Paarl mall branch.