Not a good experience with GM motores vereeniging

I am not happy with this company above(GM imperial vereeniging ), by the 15 may this year i sent my mums car to be fixed! The car can not start even nw. I sent it there couse i wanted to get the best service with profetional mechanics, bt those guys they keep dissapointing me every day couse clearly they can not fix the car, i allowed them to buy all the parts theysaid needs to be changed!so that the car can be fixed, As i am writting now , Our invoice with them is sitting at R57 000.00 (it seens as if i an buyinh onother car) bt still the car is not fixed, 1st the car is not mine, its my mums car, i am suppose to take the car to Easten Cape by wednesday bt that won’nt happen couse it seen as if evn by then there will be no good news! Firstly, i waited for the hole month for a part that was on back order, now its almost a month they did put the part, now i am getting stories of the wiaring staff that does not pass power, i realy do not understant, i phoned the manager couple of times, sometime i drive there and waist my petrol still it seens as if i am not serous, m wrried about my mother, what does she think of me, we do have money, why they can not fix? Or if possible if they can take off all the parts that they did put to that car nd return my car original parts, i wil take it some else... i feel like they do not give them enough time to have a look with that car please assist, i realy need help the car its a crueze 2014 model automatic diesel 2l.... please assist????????