I send my B class Me...

I send my B class Mercedes for diagnose after I head a sound from the front between engine and gearbox they did run the diagnose but the results was he issue of engine mountain and brake disc and I agave them the go ahead then in the 15 03 2024 I collect it then when I drive back home there sound was there I paid R15500 then on the 18 03 2024 I took it back for recheck now they are assuming that it can be a fly wheel or inside the engine I wonder wich system did they use not to see or pick this problem now I’m not sure what to trust anymore and I was charged for car wash but when I got it there were oils on the bumper I took pics and the sound is still there please assist and now is worse that before when I take it for diagnose my worry I payed but still same sound is there what was the payment for and why their system didn’t pick up this problem so they assume and put mountains engine and didn’t receive the old parts that were removed so I can get evidence if they were replaced I’m so devastated please assist