Continually Harassed for a SARS Account that Is Not Mine

Someone has *****ulently used my cell number to register their SARS account. SARS has handed them over to Nu Debt, and Nu Debt now harasses me multiple times a week on behalf of this man. I have contacted Nu Debt probably around fifteen times now by phone, and each time they remove my number and assure me the issue is resolved, but I am still receiving messages. I am concerned this man's debt is going to be associated with me due to FICA. Seeing as Nu Debt can't help me, I thought I'd go to the source. PLEASE remove my number from this man's account; you're never going to get anything back if you're sending threats to the wrong person.