For some reason they flagged your first transaction, as they may have felt it was too large for some reason (type of merchant, credit limit, etc.) Regardless, banks then try to verify that you are legitimate over the phone by asking you a series of questions they may pull from your credit report. For some reason BOA could not do this.
I would try another call to the bank, but quite honestly, they have the right to freeze/close accounts, so I'm not sure there's much you can do.
Please let us know how you ultimately make out.