Prescribed Debt

I have received a call from some one today you can hardly hear what she is saying but is threatning me to conntact me at work everyday till i pay this account which is Precribed Debt not even on ITC any more i have never had any calls from anyone till today 18/11/2015 what am i to do as i am not allowed any calls at work and could lose my job as to this as she was sayin they last called me in 2005 now after 11 year they want to call me now she dont even have my cell numberbut according to her she called me in 2005