replaced screen and digitizer in shop now no light

hi all sorry to be a pain but the weekend i took my iphone in to be repaired (local shop) was told board had gone so was scrap so asked if i could use screen on my wifes 3gs as hers had broke "yes" he said after stripping my wifes phone down he found 3g and 3gs use diff size cables and said i would have to have new screen ok i said and paid for new one to be orderd so he put my wifes original cracked screen back on but the back light did not work been today had new lcd and digitilizer fitted still no back light he then changed some coil that he recomended could be problem checked it out i said ok still no back light what could be problem cost me £45 so far and still not fixed but im damed if im going to walk away £45 down and a phone that worked before he changed screen !!!!!

any sugestions what to try would a reset do it or has he just broke my phone and owes me a new one ????