Power supply faulty ater 1 day use. no replacement

i bought a 650W power supply on Monday the 8th of June , it worked fine in my PC until the 9th of June where it was not functioning . i took the power supply back to Matrix on the 10th of June to get a refund or a replacement power supply but they said i cannot get a replacement and i am not going to get a refund . according to them it is an electronic device and if it comes back faulty it needs to be sent in to get checked ( even though they did all checks in front of me with their own equipment ) now i have been told it will take between 7 and 21 working days to come back with an answer as to whether i will get a replacement unit or if they have fixed this broken unit . this is unacceptable as i have not had the power supply long enough to even use it properly and now i must wait 2 to 4 weeks to get the broken device back from the joke of a store. these guys are actually a ******* by having faulty equipment from the first day . all proper PC stores will refund you or replace a faulty device if it comes back broken in the first week but not Matrix , they will make sure to inconvenience you as much as possible.