I would send a registered letter to headquarters of the bank, or the bank president and explain to him or her what happened when you went to the bank--include the names of people with whom you dealt and the names of those who refused to provide you with service.

Then, they will either write back and tell you why your credentials were not adequate, or he will offer you an apology for the way you were treated. I would expect an answer as to why you were discriminated against. They must provide you a reason for being declined.

Send all correspondence registered mail, with return receipt requested, so they know you are serious about getting a response.

Good luck.