Damaged Engine after engine wash!!!

I had my automatic Renault Clio engine washed by Shell Boskruin on Saturday 11 April. My car refused to start thereafter. The high pressure washer caused the water and moisture to seep into the sensitive areas of my engine. The Shell staff member failed to cover any parts and happily sprayed away damaging my multi-function switch. I phoned the garage on Sunday and spoke to the assistant manager on duty to explain my issue. He said he did not have authority to decide how Shell were going to sort it out but would call the owner and explain that a Shell staff member had damaged my car with the high pressure wash. The owner was cycling and would call me afterwards. I have received no call. My mechanic has a drawn up a report of the damage caused. This switch costs in excess of R1,800. I think that no garage should do engine washing if they fail to cover up the important engine parts that get damaged.