Ford Motomid Middelburg Mpumalanga

On the 4th of October 2018 I had my Ford focus st3 went in for it's major service at Ford Motomid Middelburg, after I took my car from them I realised that my aircon is no longer working properly, I took it back & it was fixed. A week later after that service my car had an engine check light on, I booked it again to had it checked then they told me that cylinder & spark plug number 3 is faulty so my whole engine is damaged, they shifting the blame on me and they not willing to assist me unless I buy the new engine from them which is ridiculously expensive, all this happened after my major service with them! now I'm sitting without a car! I don't know what to do, I can't even go to work because that's my only car!