Tukshop service by mumbo repairs

I recently took my car to Mumbo R from mercedes after following his tiktok however the service was not what i expected from the booking however my bigest concern is that,the car came back with a warning light that was not there before amd i noticed it after driving for 20km,upon me reporting the issue to the workshop,i am expected to pay for another Diagnostic and surely repair after.I am also told the car did not have the light on when leaving the workshop so this is a "tuckshop service"where once you leave the shop,the relationship ends.I am deeply disapointed from an MRI approved workshop and i hope this complain get to the Mumbo himself