Tomorrow we’ll finally fly to Brazil, I’m super excited.

There’s just one thing I’m thinking about:
Obviously people use Uber and credit cards in Rio.
But I’ve also heard you shouldn’t carry any valuables, it’s best to only carry about as much cash as you’ll need for day and that you should definitely never walk around with an iPhone.
But without a smartphone (I’m an iPhone user and don’t see myself buying a cheap Android phone just to be able to use Uber) - how would you order an Uber?
If there is a constant risk of theft/robbery, why would anyone carry a credit card (forced cash withdrawals etc.)?