Outsmarted and outplayed by the Paint specialist

I bought paint from builders warehouse Ysterplaat. They gave me a Cheap plascon paint in a Fired Earth 5l can. My wall is 18 sqm and ive used 3 coats on it already. My wall is 3 different shades of grey and if i try and clean the wall i rub the paint off. This is after a week of the wall being painted. I took the paint back to them so i can get a better quality paint but they refuse to refund or replace the paint. The paint specialist said he gave me a cheaper paint, but they didnt mention to me that the paint was such poor quality. Outsmarted and outplayed by the Paint specialist. I will buy new paint elsewhere