About changing phones
What to do if you get a new phone, a new number, or both.
HiYou has a different path depending on what actually changed.
New phone, same number
Install HiYou on the new phone and register with the same number - it signs you straight back into your existing account. See How to register your phone number.
To also bring over your chat history once you're signed in, see How to transfer chat history to a new device.
Same phone, new number
Use How to change your phone number. It keeps your account, chats, and groups exactly as they are - no re-registration needed.
New phone and new number
Register on the new phone using your current number first to get back into your existing account, then change your number from inside your profile once you're signed in.