Firstly, read "How to Win Friends and Influence People". There's a good chapter on letter-writing.
Secondly: write a polite and short letter addressed directly to the Chairperson of the financial institution. They don't want the hassle and/or exposure, especially if you have a strong case. (This has worked for me personally and a number of others whom I know.)
Thirdly, the financial regulator might be worth a shot if the Chairperson letter doesn't work.
No bubble burst re customer care and ethics. I will always try to believe in or see the good part of anything (including banks).....thinking that everyone is out to con or rob me is too depressing.
Well back to my book......where was I? ah Once upon a time.....
I could be wrong but I think BOI took over some of ICS products about a year or more ago. I seem to remember getting a letter about it, but getting a better deal somewhere else and switched rather than continue with BOI. If I remember I'd dig out the paperwork later.