BILLED for job not done!

After 320d Broke down, I towed the car to fors****s bmw in pinetown. I was told to pay R1900 for a diagnosis on the car to find the fault. Today I get a call stating that I must pay R10000 to strip the engine in order for them to find the fault! What kind of bmw agents cannot find the fault but wants to charge the customer R1900 for a diagnosis? So what am I paying R1900 for????