iPhone help

[CisMyArse]

I have an iPhone. I bought DD an iPhone 5 when she started comp and it's linked to my iTunes.

My 2 year contract is up and I've been sent an upgrade (5s to 5SE). SIM card is in. I've connected it to my iTunes and it's downloaded everything from DD's phone instead of my existing phone. As a result I'm
Still using my old phone.

How do I sort this out?
When will my new phone start working and my old phone stop working? Am I paying for 2 phones??!

I am phone-thick.

Bump

When you set up the phone I'm sure there's an option to retrieve a backup and it has a list of each device that has been backed up on your account. Can you reset the phone and then retrieve the correct backup?

Best thing is to have your daughters setup with her own Apple ID and use Family sharing. Then backup your current phone, reset your new phone and restore from backup.