Ordering online but still have to wait in a queue

I ordered online for collection at the Nandos Plattekloof outlet. On arrival at the store I waited 30mins for collection. Why order online if you still have to wait 30mins your in a queue to collect. I phoned the manager of the store who told me he was helping in front and there was no queue. What made it worse that there was one cashier only. While speaking to the manager he just hanged up while I was talking on the phone. How rude!! Will not go back there again.