OVERCHARGED - REFUSES TO REFUND

I ordered aquarium supplies from Online Petshop. The parcel was packaged, measured and weighed by Hettie Moolman and these dimensions were sent to me so that I could arrange my courier to collect. Hettie Moolman mistakingly informed me that the package weighed 27.3kg instead of 2.73kg. As a result of this, the courier company overcharged me for the parcel. Hettie Moolman was given the opportunity to fix her mistake and refund me the money. Instead, she has merely forwarded my query to the courier company for me to deal with. I am now in a state of frustration trying to fix her mistake with the courier company. All I asked was for her to fix her mistake, instead, Hettie Moolman expects me to carry the cost for her mistake. The courier company is refusing to refund me, stating some weird and unreasonable reasons. This is why Hettie Moolman must refund me for my loss to save me the pain of fighting for my money. Save yourself a lot of grief and stay away from Online Petshop, their attitude and policies are quite offensive.