Credit Company or ****?

I am being harassed (up to a year now) by this company for a payment which I have no knowledge what it is for. They are claiming an amount and sending me bank details. I have provided ALL the invoices and proof of payments that I have for the service provider they claim I did not pay. I further requested they provide me with more details - in the case that my records could be mistaken. But they have ignored all my correspondence and continue to send me emails. What do I do? I am hoping that they will respond to a Hello Peter review.