7/11 citi ATM fraud

I know this is a long shot … But maybe someone has had a similar experience. I withdrew money from a Citibank branded machine last week in a 7/11 on Fulton which is something I do about once a week. Four hours after I did the withdrawal another withdrawal was made, but it wasn’t me. Now Citibank does not accept my claim because they say ‘my card and pin’ was used. Nice company! what would you do to get the money back – it was $400 which is the max the machine will give in one transaction