I'm Aussie based and plan to use Uber on an upcoming trip to South America and the USA. I won't be using global roaming as it's very expensive here. So assuming I can order an Uber using wifi, what happens if the driver tries to call the number and no one answers? What if they can't find you?

When you order an Uber using wifi, is there a comments section where you can tell them you don't have a phone and where they can find you?