Have you moved and not informed your creditors about your new address?
This is the recipe for a Backdoor CCJ /phantom judgement - where a court claim is issued against you and you don't find out about it until a judgement has been given against you and you then find that the debt collectors/bailiffs find out where you really live.
If you change address, inform your creditors. Don't think that by not informing creditors you will avoid trouble.
A Backdoor CCJ will find its way onto your credit file and spell at least six years of a blighted credit history.