抱怨没有用得拉。难道你要去告法官嘛？ 再说了，银行口头承诺也可以有效啊。

with proper consideration and bargaining, oral agreement could have binding effect as well. 

If you bf can show that he reasonably relied on the bank's oral promise and suffered huge financial loss, he can also sue for estoppel and restitution damages.