Terrible shocking bad service

On 31/03/2015 took my car to west cape vw(kuilsriver) for a 180k service. I was asked if there was any additional things i would like them to check. I therefore asked for unusual high water usage to be checked as i couldn't find any leakage and other things. They contacted my wife during the day just to say they still busy with the car. Around 16:30 i phoned them and i was told my car is ready. To my suprise they only did the norman service and none of the things i asked them to do were done. I was told i have to book the car again if i need any additional things to be checked. Why did they ask for additional work to be checked if that is not part of work. They said they cant spend the whole day on one car. The same day i took my car home i got the check coolerant indication and i had to put water as usual. What must i do?