If you can get no satisfaction from the local branch manager, bypass the minimum wage workers and go straight to the CEO. Complaints on their twitter and Facebook also get attention. Or complain to the Office of Thrift Supervision which is part of the Office of the Comptroller of the Currency. The OCC's Consumer Assistance Group assists national bank and federal savings association, or thrift customers.
There is something that you can do in order to clear the issue with the bank. Talk to the customer service attendant at the back to find out what is causing your checks to bounce. Once everything has been made clear, you can ask for the options that you have in redeeming your credit.