Terrible Service

I took my Tiguan in this year end of May for its annual year service. (note that my car has not been giving me any issues, this was its standard annual service). My service provider phoned me to advise that they detected a small crack in my thermostat housing, and that it needs to be replaced in order to prevent it getting worse, potentially causing coolant leakage and engine damage. I agreed to have this replaced (at a cost of more than R17k). Just over a month after receiving my car back, I received a "coolant level too low" warning (which has never happened before). I filled up the coolant, but two weeks later I received the same warning, and upon checking confirm that it was once again empty. I contacted VW tableview explaining this, and they told me to bring the car in the following Monday. I checked my car in on Monday, and, long story short, it's 4 days later and I still have NO feedback on what is wrong, or when I will be receiving my car. I've phone multiple times daily, and they always promise to get back to me, but they never do. My last attempts were with the service consultant's manager, and she is also not getting back. I now tried to speak to ANYONE that can assist, and after the receptionist put me through to 4 different people (none of which answered), my call got dropped. I tried phoning VW head office, been holding for 15mins, but no one is assisting.