Nudebt harassment!

Nudebt have been harassing me via email, sms and calling about an outstanding COJ account that doesn't belong to me. I confirmed this with COJ. Nudebt cannot produce any supporting information that links me to the account whatsover (they hardly have any information at all!) but they continue to harass me, calling my office today to find out when our pay day is. I am not sure how they got my details in the first place! I dont know if this is a **** or if they seriously think I am the right person to be chasing for money!