Rude Call Centre Agent

I received a call from Private number from a call centre agent selling MTN data. Upon mentioning that I am not a MTN customer, he tried to sell me something else. He had called whilst I was working and refused to listen when I said i was busy at work and was not interested in buying any data (He started talking over me). After mentioning again (for the fifth time) that I am not interested and I am busy at work, he stated that he knew I was busy but he needed a few minutes of my time. Usually when you tell someone that you are busy, they offer to call at a more suitable time. I repeated what i had previously been stating and he mumbled rude words under his breath. When i asked for his name, he proceeded to cut the call. I then got an sms from Yello mobile stating the following 'Thank you for your interest in Yello Mobile. We will keep you updated on our deals and specials. For queries, please call ***. The Yello Mobile Team\.<br> <br> Let it be clear that I AM NOT INTERESTED in your products. Please train your call centre staff properly and deal with the agent that had spoken to me. If all your calls are recorded I would hope that you will listen to each call and find the culprit!"