Rude callcenter agent

I was just phoned by Smart Mobile (agent's name was Lindani) offering me a cellular contract. In the first place, I never consented to being contacted by Smart Mobile or any other such service. And further to that, when I attempted to explain in as friendly a manner as possible that I am not interested and that I would be wasting Lindani's time, he simply put the phone down in my ear.

This is utterly appalling behaviour and I am starting to understand why other people are rude to cold callers.