SunTrust Bank Bank Account Or Service Complaint

SunTrust Bank Bank account or service department,

Checking account Deposits and withdrawals Maryland

Having problems with suntrust bank. Made a deposit including a check and $500.00 in cash, have the deposit receipt. The amount was credited to the account next day. Week later theyWithdrew the $500.00 and Said i never made the $500.00 cash deposit. Requested to see the -The bank told me it is only for their own use. I think they are trying to cover up their mistake. How do i get my money back?