POST OFFICE PICKUP COSTS

I am lost for words! I am a student that sell products to make some extra money so I can help pay for my studies. I ordered a parcel, (barely made R500 profit) and when I went to the post office to pick it up, they told me I had to pay R3400. It was reevaluated and the amount remained. (Reevaluation took another 2 weeks while I already waited 3 weeks to go through Johannesburg clearance) They had a terrible attitude, not willing to help AT ALL. They don't want to show me how the amount is calculated either. I had to pay half of the money I paid for the products to the post office.