wont accept a return & sold wrong parts

Used then once before with no problems. second time i used them they sent me the wrong oil filter even after i had specified the vehicle details and registration number.
now they wont accept a return saying that i should have checked the dimensions of the filter before i ordered it. Would love to know how to do that when the oil filter is covered and in use. (What is the point in giving then the vehicle details etc etc). Went to my local garage and they sorted me out with the correct part and cheaper than CP4L. Will go there next time.