Mercedes Benz polokwane poor service

Very unprofessional and don’t know what they’re doing.Took my car because it had an engine light on,they replaced the battery and when it came back the fuel flap wasn’t opening.A week later the engine light came back on again,took it back this time,they had my car for over a week,replaced pressure sensors and thermostat.Picked it up and drove 50kms and the engine light came back on again.