United Bank Of India [UBI] — unwanted debit from account during internet banking

Website: ebank.unitedbankofindia.com

On 25th december, i was using internet banking portal o[censored]nited bank of india. I was trying to pay of 4000 rs.in another bank account o[censored]nited bank of india. Due to some technical problem, the beneficiary bank name changed to union bank of india during payment. Although i have seen a message showing "the transaction has been declined" in the computer screen just after the transfer attempt, 4006 rs. Has been deducted from my account. I have also received the same message in my mobile.
The mobile message is attached herewith. The imps ref no. Of the concerned debit is[protected].
I have also attached and a mini statement of the account. The 2nd transaction (Serial no 2) is the transaction in concern.

Detail of the bank account (Debited)

Name of account holder - sayan majumder
Branch - bckvv branch, united bank of india
Account no.[protected]
Ifsc code - utbi0bckc16 (The 5th character is zero)

Details of the bank account (Beneficiary)

Bank - union bank of india
Account no[protected]

For, correspondence - e-mail address - [protected]@gmail.com
- mobile no. - [protected]