Frauduant default on dredit report

dan19030

I'll try to keep this quite short. I have a default on my credit report. I had reported to the company that this was fraud and provided them with all the information I have about the debt including a crime reference number from the police. They have since put a default on my credit report. Can they do this after I reported this as fraud? This same debt has already been dismissed by another debt collector and recognised as fraudulant. Any help or advise would be great.