Poor Service delivery

I took my car for service , but it came back leaking oil , i contacted service manager, henk faber , i brought the car back to them and they found out it was leaking oil, but henk faber told me is not their fault or responsibility but i told him i brought my car faultless for service and you did change the oil then after, is leaking oil , who shoul i blame , he was very rude and aggressive, , i admonish my fellow brothers and sisters if you take your car there for service or any mechanical issue you take it at your own risk.