Poor service delivery

Ordered a product 900g, it was scanned correctly, I was billed for the 900g, however received 600g. I called the help centre, they told me I can request a refund/credit, but was told it will be declined. I was then told to take the product back to the store, to exchange it or request a refund (at my own cost) rectifying a mistake made by them. Paying for a delivery, then I need to travel back at and additional expense. This is poor service. I had to ask for a delivery fee refund, the did not even offer to refund it. Just saying we made the mistake sorry for the inconvenience. Now I can't even use the product.