Paid for 1 bag 3 TIMES

Upon changing the flight, I paid extra for my bag when I made the change via telephone. When I arrived at the airport (Jhb) they had no reference of this. I had to pay AGAIN. When I left Cpt today, again they had no referencr of either of the luggage pieces already paid for. AGAIN I had to pay for the luggage. This is unacceptable. You are running a cheap taxi service, not a low cost air service