The Courier Guy Overcharges

I booked 2 parcels for local collection and had enough funds in our COD account. Then they sent an email saying we owed them money. The actual weight of the two parcels were 9.1kg, but we are being charged for volumetric weight of 33kg's. Why do they even bother giving you a quote? We paid for Same Day Local, but because we owed them money, the parcels were sent back to the hub. It seems their support service people only work until 5 o'clock as they have been sending me emails, but now I don't get any reply. It would have been cheaper if I had collected the parcels from Durbanville myself. I would not have driven out R500's petrol.