Manager failing to take responsability

I drove in the above mentioned fuel station to fill up my tank for fuel tank and bought 2cans of oil.Then I drove out to work as I use my car for chauffeuring services (with Uber as well).I drove the car for4days and it started stalling and showing strange light signs on its cluster and developing a strange idling as well.Only to find out that the attendant never replaced the oil lid.So I went back with another car to report this my case was handled by Lawrence (Branch Manager)and we checked together on their own cctv cameras only to find that it does show that they are responsible for this.Our agreement was to take the car in to AUDI Center where I always take my car for service to have it checked to see if everything is still in order since the car drove for days and flashed all the oil out of the engine.And I was quoted R2166.Now Total Service Station refuses to take responsibility and they says I must use their backyard mechanic for this risk check.I never used any backyard mechanic for my car and I WILL NOT DOIT FOR ANYONE I AM AWARE THAT THEY WANT TO MANUPULATE THIS EVEN FIRST TIME BUT THANK GOD THEIR VIDEOS PROVED THEM WRONG.AND I AM GOING TO TAKE FURTHER LEGAL ACTION.