Absolute rubbish

Used Dulux Once Matt Emulsion to decorate the entire house in the summer. A few weeks later I noticed a small mark on a wall, so I got a damp cloth and gently dabbed it. The paint came straight off down to the previous colour. I complained to Dulux. They asked for samples. Weeks later I had heard nothing so phoned their help line and was told the samples has passed all their quality control tests and there was nothing wrong with them. It must be my fault - bad application, preparation etc. Not true. The representative did say that the paint can take 3 months to "cure" properly. Where does it say that on the tin? Anyway, I have now noticed a previous mark where a picture hung starting to show through. What is up with this paint? It is total and utter rubbish, and I cannot believe Dulux are getting away with this. I will never, ever use Dulux paint again and I tell everyone I know to avoid it. Please spread the word. They need to admit there's a problem and do something about it.