Some banks require you to inform them securely online if you're going on holiday and plan to use your ATM card there - for your security. This is done by UK banks for example. I can't speak for US banks.
Typically they'll ask the country destination and the dates you'll be there.
So, if your bank uses this system it's probably too late to do it online as you're already there and they'll be a limit as to how late you can inform them. Therefore, you'll need to call them, answer security questions, and be able to gain access to funds the next day.