I was travelling in Australia some years back and went to use my Kiwibank mastercard only to discover it has been locked by Kiwibank for suspicious transactions. They had not notified me and I discovered it outside of NZ working hours, so couldn't talk to anyone at Kiwibank at the time. To say I was pretty p***d at the time was an understatement. It turned out the suspicious transactions were numerous Amazon transactions (I was buying a lot of DVDs back then).
That said, Kiwibank have been pretty good ever since. I use them for all banking and service, in general, is excellent. I've also had fraudulent trades on my Mastercard in the past - I completed the form and Kiwibank credited the money back promptly .