Hi there, whilst there is nothing stopping a party from pursuing what they believe is a genuine debt, if there is clear evidence that his is not true and they are pursuing you unreasonably, it could eventually amount to harassment, which could be both a civil matter and a criminal one. The law states that a person must not pursue a course of conduct which amounts to harassment of another and which he or she knows or ought to know amounts to harassment. Although there is no definition of what specifically amounts to harassment, it would usually include alarming a person or causing them distress and must have occurred on at least two occasions.
Under criminal law, and if this is reported to the police who then take action, the punishment for harassment can be imprisonment and/or a fine. A court may also impose a restraining order for the purpose of protecting the victim.
In addition to criminal action, a civil claim can also be brought against a person who is alleged to be guilty of causing harassment. The courts would award compensation to the victim, something that is unlikely to happen if this is pursued as a criminal issue.
So in the first instance the police can be contacted and this matter reported to them as harassment. However, they will not often get involved in trivial disputes so if they believe that this is not serious enough they could refuse to help and advise you that this is a civil matter. In such circumstances, the victim can warn the harasser that their actions are being treated as harassment and that unless they refrain from such behaviour in the future they will be reported to the police and legal action under harassment legislation taken against them.
In terms of your credit rating this should not be affected until they go to court and only if they win and you do not pay within a month of being ordered to do so.