How to kill a customer

I've been a happy, loyal Cell-C fan for years. ...until recently.<br> <br> Cell-C are harassing me with phone calls where the call-center agents try all sorts of nasty tricks and games to get me to commit to another 24 months, and they refuse to stop calling.<br> <br> Here's the thing... I was a happy customer - and had planned to keep all four SIMS active permanently - but who wants to support a business that tries to trick and harass it's own customers?<br> <br> Asking the agents to make a note not to call in future doesn't get them to stop calling.<br> Hanging up doesn't get them to stop calling.<br> Even being damned rude and hanging up doesn't get them to stop calling!!!<br> <br> Surely it costs money to have agents calling otherwise-happy customers and harassing them into a state of dissonance? Does Alan Knott Craig know that his agents are chasing away Cell-C's customers?