Complain

I took my car in to Hyundai edenvale on the 19/01/2018 to have it diagnosed bacause the car was cutting off while driving,it was found that the was a problem with the crankshaft sensor,and because i have a warranty i was told they will fix it under the warranty but they didnt have parts and that they wil call me to bring the car back in,my service book was taken on the 19th and they did not give it back,i called in to tell them i did not recieve it they said they would have a look,the call me to bring the car back on the 5th of February,the car was fixed but my service book was no where to b found,i want my service book back,they lost it and i want it