Restoring new iPhone 5S from old phone back up (iOS 7)

You would need to have the exact same version of iOS on both devices.

So if your old 5S had 7.1.2 (the latest version of iOS 7), then your new phone needs to at least have that same version or something newer.

Unfortunately, you'll have to choose between restoring your backup & updating to iOS 8, or losing your data unless/until you choose to upgrade & restore from the backup.

~Lyssa

I have the same problem with my new phone, my old phone is updated to iOS 8.3 but the phone i have just purchased must not be as updated. Am i able to restore it as new and the back it up later?

If your new/replacement phone isn't up to date, here's what you can do:

1) Set up the replacement phone as new & complete the update

2) Once you're finished setting up the phone, go into Settings>General>Reset and choose Erase all content and Settings

That will put the phone back in its original state & you can then restore it from a backup.

~Lyssa