You should adopt a multi-pronged approach.
First, gather all your documentation, dates, who you spoke with, etc.
.
Second, put all facts in a well-organized, business letter.
Third, research to find the names & address of:
1. Highest ranked person at branch of bank that you
made initial request to tranfer funds from.
2. CEO and/or President of Home Office of bank in
1. above
3. Head of State Banking Commission
4. CEO and/or President of Home Office of bank
that funds were transferred to.
Fourth, send well-organized letter from 2nd step to ALL people identified in 3rd step above. Be sure that .cc at end of letter shows all other people the same letter went to.
You'll be surprised how effectively peer pressure can work in a situation like this.