The reason for tax deducted by Bank @ 20 % is you have not provided copy of your PAN card to the Bank (or the bank may have lost it but no one agrees)
Solution :
1. Provide copy of your PAN Card to Bank
2. Ask your Bank for submitting Revised ETDS Return for A.Y.2010-11
3. Get TDS Certificate from Bank (Reason is to ensure bank has submitted revised etds return)
4. If you have filled your Income Tax Return for Financial Year 2009-2010 within due date and you have not received Assessment order yet, then you can file your revised income tax return.
5. Before filling revised income tax return for F.Y.2009-10, please register and view Form26AS, to ensure you have got credit for TDS @ 20% deducted by Bank.
Please consult practising chartered accountant for proper advise.