Wrong product received from online shopping

I bought a product online on a 40% off sale. They have sent me the wrong product. When I informed them they said they'll do a refund and to say sorry they'll give me 20% off on my next purchase instead of sending me the product that I ordered. So at the end it's me losing and it was their mistake.

This is the 2nd time they got my order wrong.

Won't support them again and will get the word out there.