Stop calling me

I keep on getting called by their call centre and they do not put me on their do not call list, I sometimes get called every day of the week and on some days twice a week. I have asked to speak to a manager but get cut off. I tried to call the call centre back but get cut off. I am getting ready to take legal action should the calls not stop, and I get an official apology. This behaviour is ******* and is an infringement of my rights.