VW Fourways swap your Tyres for Old worn out ones

I took my car in for its annual service at Lindsay Saker VW Fourways and also did a wheel alignment and balancing. After I fetched my car from them a Loss of tyre pressure message appeared and I decided to actually check my tyres only to realize that my back tyres were exchanged with worn out tyres. With the low kilometres that I have it is not possible that my tyres would be this worn out to this extent and I had checked them before taking my care to the dealership. I have since told called VW on Monday to lodge my complaint and they said they will call me back and to this day they have not called me black. It is so disappointing that after 4 years of servicing my car with them that they would take advantage because I am a woman. Their customer service team called me on Monday and I told them about my tyres and they said they would let them know in order to resolve this matter. I did the wheel alignment and balancing so that I do not have issues when travelling only for VW Fourways to put my life in danger by exchanging tyres with old ones.