Shocking harassment by "debt collectors""

Keep getting called for a Telkom that we have told them has been settled. A very rude Vukilo Mzizi called me today. The account is not mine. Then she demanded I give her my husband's number (she didn't even have the correct initials). Was rude and aggressive. I am seriously angry about being harassed like this. We don't owe any money to Telkom (have written proof of this) and yet still they call. And during my work hours! Harassment is not acceptable.