Shapiro Shaik is harassing me. And jeopardizing people's lives

This company is harassing me with a debt payment that I have completed. They even call me on my work line harassing me even when I have explained to them that I work at emergency roadside and we get accident clients calling in for rescue so they are basically jerpadizing people's lives. I don't even know how they got my personal work line but they surely adamant on getting money from me, money that I am no longer indebted to... If you can't help me please advise what I must do because they are making my life miserable and now it is starting to affect my job and other people's lives.

Thank you

Kind regards Lerato. N