The safest action to take if someone claiming to be from your bank calls you to ask for account information is to

Cutting the call and calling back through banks official number

Explanation:

According to the mentioned situation in the question, if someone calls regarding gaining any sort of bank account information claiming to be your bank, the best step is to assure using the banks official number.

You should immediately hang up the call and then call back by using the authentic number provided by bank .If the person was authorized caller then it will get clarified through the call back as only genuine bank employee will communicate through that number .

If any false call was made to gain account information  for misuse ,then it would be identified.