Charged mass 80% more than actual mass

A family member of mine got a quote from The Courier Guy to transport 3 suitcases from Johannesburg to Cape Town, after sending them the dimensions and mass of each. The quote was reasonable, it was accepted and paid, the suitcases were picked up and transported. Afterwards my family member's account was charged with extra cost based on so-called charged masses. The Courier Guy's actual masses for the 3 suitcases agreed sufficiently with the masses that were sent to them for the quote and the required upfront payment, but the charged masses were roundabout 80% more. Their quote mentioned nothing of any extra cost that would occur. Based on this, The Courier Guy's service is terrible, dishonest and an exploitation.