Mileage drop after service

Hello Sir ,
This may seem weird but it’s true that mileage of my car has dropped after service . I recently got my Vitara breeza (diesel) serviced . Air Filter , Oil Filter , Air Conditioner Filter was changed along with engine oil. Wheel alignment and balancing was also done after service.

Did service mechanic missed something while doing service ? I can see a big drop . Earlier it was 20 kmpl and now after service mileage has dropped to 15kmpl .