Many people are afraid of cryptocurrencies because they heard about people losing all of their Bitcoin when they lost access to their wallet. What happens to my money when my phone is damaged?
Your IOTA are not stored on your phone, they are stored on the decentralized tangle. Your seed is your password to access your IOTA, anytime, anywhere. As long as you have your seed saved in a place other than your phone, which you definitely should, then you will be totally fine.
Nothing because your IOTAs aren't on your phone.
This is true with any cryptocurrency really.
All that you may have on your phone is your seed. And in iota, your seed is what is used to deterministically generate addresses which contain your balances. With your seed, you can then sign a transaction to move value on the network.
In theory, you can just memorize your seed, and your money will then follow you wherever you go, phone or not.
IOTA balance is stored on your private seed, not your phone.