Car city service, worse company

I regret taking my car to car city service. I'm driving a polo 6 and I have never missed a service. I always see post in the street how cheap is car service, don't let them fool you. I took my car for a service at four ways and they quoted me 11k which I did paid. Biggest mistake in my life. The employees there are extremely rude especially the ladies. After collecting my car on the very same day on my way home the heater was not working anymore, I called them the next day. I was told to bring it in of which I did. I collected the car again later that day and I was told its now working, on my way home the same issue stated. For 11k this is the service I'm getting!!! My heater was working 100% fine until tmcar service city did their 72 point check and I was told I must change my heat valve and thermometer which I gave them a go a head. Now my vehicle temperature drops to a minus and don't have hot air blowing in to keep me warm. Car city service is ****ed up. If they can't fix my vehicle to the same condition it was, they should tell me!! And take out their parts and put back my old parts then my heater will work fine and refund my 11k. Should they fail to do that... I'm involving my lawyer