Old Mutual harasment

Old Mutual has been harassing me for months to get my husband's cell phone number. I have asked them many times to stop phoning me. They use the number ***. The do not want to tell me why they want to speak to him and I will thus not give out his number to be harassed like me. Yet they don't stop phoning. I am sick and tired of this nonsense. I just want them to stop bothering me.