How can I make the IR understand me?

I have problems with the IR demanding a refund of Children's Tax credit when no money is actually owed.

Last June when I went from employment with a chemical manufacturer to employment by my own company, my wife informed the tax agency that my income for tax year 04 to 05 would likely be lower than 03-04. The authority made a mistake and stopped my tax credit.

They subsequently spotted the mistake and re-started the credit. A few weeks later I got a request for more information. I responded by phone and for several months kept getting and giving the same request/information. All along various staff have told me on the phone that I have nothing else to tell and nothing of concern.

But I then started getting letters saying I owed over £100 in overpayment. I was sent a form to fill in to "appeal" against the supposed owed money, which I filled in. Last weekend I got a final demand saying I have to pay the "owed" money by March. The staff continue to tell me I owe nothing. But they appear to be unable to stop this demand for money I do NOT owe.

The latest development is they are sending me yet another appeal form. So around the loop we go again. But they still are unable to put a "hold" on the demand for money. All the calls and letters are apparently shown on the IR computer system so they don't dispute the true facts. What can I do to finally make them understand I don't owe money?

Any help appreciated I am at the end of my tether and on the verge of paying the money despite not owing it.

Regards