I can enable or disable an individual credit card using an app on my phone in 30 seconds. A large proportion of my customers leave their cards locked by default and then unlock it for a minute when it's time to pay for something. I promise you that a corporate account has something similar. You don't need to call the bank and report fraud every time you do this, just disable the card from the customer control panel and then re-enable it when you get your invoices. This never needs to even involve a bank employee unless you really do have a real instance of fraud that you then need to backcharge.