Claiming of tds @ 20% without pan

1.Any person deducting tax (PAN available or not, higher rate of 20% or regular rate) is bound to issue TDS Certificate u/s. 203 of the Income Tax Act.
2.The fact the you had not provided PAN at the time of deduction of tax or filing of TDS statement by bank DOES NOT exempt the bank from issue of TDS Certificate to you.
3.Since your tax has been deducted and paid to the government treasury, you are legally eligible to get credit of TDS, whatever being the rate, 20% or anything.
so, approach the bank intimating your pan details to them and obtain tds certificate and file return to get refund

You have to do some running around, get to the bank officials and ask them to file return after your pan is updated with them, once you have enough proof of TDS payment, you can also meet your AO.

do u think bank will revise its return for a small customer?

Bank won't help you .. .

is there any other way to claim refund?