person claimed to be from Mastercard and Visa support (servicing all major banks)
then told me i had 6 x $860 online transactions on my account today (not true)
repeatedly asked me to tell him what device i was using to check my account balances ( i refused to tell and asked why it mattered)
told me that he wont ask for any bank details but needed to confirm i didnt authorise the transactions. (didnt even mention my name at any point in the call, weird)

i asked for the number to call him back and he told me he was on the number that is on the back of my card. so i hung up and called me bank directly