Cannot positively identify me

I have an iStore Card and I phoned the call centre to update my payment options. They asked me security questions and lo and behold they couldn't identify me positively. They couldn't further assist me at all and even logging a complaint I was assure, would not make them able to assist me. That is absurd. If I answer questions truthfully and they cannot positively identify me, the problem for sure is not mine. Now I cannot even cancel the card without going to a branch. I am beyond disgusted.