Lack of professionalism and customer service

I requested by email a statement detailing interest earned on my transmission account for tax year ending Feb 2015. I was told that i need an authorisation letter. I have requested where do I get this letter, what form must it take etc.<br> <br> In 5 emails I have repeatedly been told (in various ways, this being an example ):<br> <br> \Please note if you are requesting something you put the account number