Harassing call centre agents with an attitude

If only it was possible to not give any star. Why are your call centre agents harrasing me and speaking Zulu on the other side of the line as if every black person speaks that language. Surely I have a right to ask for them to stop calling me? I told two people I don’t want insurance and guess who the third call was from? The guy speaking Zulu again. Maybe if you guys had reasonable premiums then you wouldn’t have to harass us with calls like this. We have cheaper options and this just put me off your company forever. I need to know how I can make sure you never call me again even in the future.