Change in requirements when a call reference is requested

A login occurred to my internet banking. The consultant advised me it was a bank error & sent by mistake there was no activity on my account (he assures me the conversation is recorded). When I asked for a reference number - the bank now wants to cancel all my cards and delink my internet banking "to be safe' - none of which was required until I asked for a reference. This is unacceptable. How does the "story" change when references are required?