'Our directors don't lower themselves to speak to customers!'

I have had a substantial sum of money with this institution for some time. Suddenly, they wouldn't accept deposits from me. Apparently they told me it was because I hadn't provided documents which they hadn't yet requested! Then I was told I could cancel my account! I jumped at the chance, but when I followed the steps to do so I found I couldn't do that either! My own building society has ****** my funds and there is nothing I can do about it!