Failed to make payment

I have recently went to a pick n pay in Soweto Tseles and had a challenge in making a payment via the Fnb tso and pay application, this is not the first time I have tried to perform this type of payment at this store, the first time i tried to make use of this payment method there was a dispute that took place but eventually allowed me to make payment. On the 27th December 2018 I was denied to make use of this payment and as a result I couldn't get my groceries. I'd like to get clarification around this issue because it becomes an inconvenience for me if in other branches I'm able to use this type of payment while at this 1 store I am unable to. I'd like to believe that pick n pay is governed by the same policy and rules and therefor expect to get the same treatment across.