Account not mine but getting threats ict listing

On the 23rd of February 2015 I received a call from ICT in Cape Town, notifying me of my \outstanding"account with Lancet and me being blacklisted. I was told that I signed for responsibility for an account for a Mrs. Havenga at the hospital in George last year May. I told the person on the line that I am not responsible for Mrs. Havenga nor do I know this person in question. She told me to sort it out with Lancet. I contacted Lancet immediately on the number supp**** by ICT and was told by the account department that it is a mistake as my number is not listed on their database. They will delete my number as the account is definately not for me. Again I received a phone call from ICT and I told them they are making a mistake and must contact Lancet. Again I received a call from ICT demanding that I pay the R1500 outstanding. I contacted Lancet again"