Trust Relationship Broken

Ok so I have lost faith in the workmanship of you guys completely my car has recently been for a services and not more then two months ago I can be corrected if they stamped my book at Kia Motors Fourwayswhich wasn't done even after being called to rate the service and advised of how disappointed I was,non the less as I was driving yesterday my car breakdowns thank God in front of KIA Roodepoort I am told they are not sure what is wrong with my engine and it's required to be stripped as the headgaskit may have blown,please note this has happened before because of @KIA Motors Northcliff now I am being told it will cost R7000 to check, if I decline I pay it if I accept I don't pay it like what more frustrating experience must a person go through with a car from KIA Motors South Africa Africa, what must a person do to get things done correctly and professionally the first time around? this I will rave and rant about till I get answer I'm exhausted.And please note they have recently had to repair my car because of a mechanics negligence which I warned Neil about that if this little incident causes further issues I will not be the happiest of people.One last note on my last service I was told there is alil leak but it's nothing to worry about which I questioned and I was advised it's nothing to worry about.Should I require this to go as far as referring to the Customer Protection Act I'll will go that far.