AUDI HATFIELD WORST EXPERIENCE PLEASE GIVE ADVICE

I booked my vehicle for a oil service at Hatfield Audi in Pretoria. After receiving my vehicle back from Audi I asked the technician that serviced my vehicle if everything was fine and he guaranteed me that everything is 100% the diagnostics showed no faults. I took the vehicle and drove home. The following day I had a wedding to attend in Potchefstroom I took the trip with confidence as my vehicle was serviced the previous day so I was looking forward to take on the long road. About 170Km in to my trip it all went wrong my vehicle cut out no function with a warning indicator of OIL PRESSURE LOW my vehicle dead cant start nothing. I was confused as my vehicle had a oil service the previous day at Audi Hatfield and now this. I phoned Audi the following day to explained the situation and they simply said sorry sir it is not our fault. So I asked the technician that did the service on the vehicle for the diagnostics that he did before servicing my vehicle and he said he will print it for me. When I went to Audi to collect the diagnostics report the technician now all of a sudden told me he cant print it as it was deleted of the system. NOW I ASKE WHY WAS IT DELETED ??? PLEASE ADVICE