Unauthorised NBR SUB FEE DEBITED ON MY CHEQUE ACC

Reported ref ***/02 about an unauthorised nrb sub fee on my Cheque account. Was told it has been escalated. Received ref *** from Bank on 07/07 about the state of my account from collections department which I told the Consultant was caused by the reported query. Contacted Bank via Customer Service by mail & phone which I was told IT is investigating the matter. Bank responded on the 09/02 and was told my query has bn given priority with ref ***3. Constantly I get calls from collections and I'm tired of being explaining the same thing. Contacted bank on the 18/02 and Consultant promised to come back the next day as a result of unavailability of Snr Management. On the 19/02 was told my query is with Snr Management. But how does that help me cause 21 days has gone bye. How can I guarantee safety of my funds in near future if they can't able to explain. I am seriously considering closing that account.