Inexperienced salesman

I bought parts on three occasions and the salesman gave me the wrong part.i had to go back to exchange the parts and this wasted my time and It cost me money as i used more petrol because of this.i don't think that the salesman know what they doing there. They need to be trained properly, they are inexperienced. I'm sure that if you bring them a sample of the part they will still get it wrong. I will not buy parts again from them and i suggest that anyone thinking of going there must rather go somewhere else.