Q: I changed my apple id. Signed out of old one and into new one, all iTunes stuff transferred over no problem. However iPhone has since run out of storage. Can't back up to iCloud as iCloud still has old Apple ID and I can't change it. Help!!!

Hello there,

Thanks for using the Apple Support Communities.

From your post I understand you've changed your Apple ID username, and you are now unable to use iCloud on your iPhone.  If you are being prompted to sign in with your previous Apple ID, you will need to follow the directions below to temporarily change it back to your old Apple ID.

Change your Apple ID temporarily

Use these steps to change your Apple ID temporarily:

1. Go to My Apple ID, click Manage your Apple ID, and sign in with your current Apple ID.
2. Select Edit next to Apple ID and Primary Email Address. 
3. Change your Apple ID to the email address that iCloud is asking you to sign in with. You shouldn't need to verify the email address.
4. Sign out of My Apple ID.

Then sign out of iCloud on your iPhone, iPad, or iPod touch:

1. Tap Settings > iCloud on your iOS device.
2. Scroll down and tap Sign Out, then tap Sign Out to confirm. If you're using iOS 7 or earlier, tap Delete Account, then tap Delete to confirm.
3. Tap Keep on My [Device] or Delete from My [Device], and enter the password for your Apple ID. Your data remains in iCloud, and it will be updated on your device when you sign in to iCloud again.
4. If you're signed in on more than one device with this Apple ID, repeat steps 1-3 on each device.
5. Go to My Apple ID, and sign in again. 
6. Change your Apple ID to the email address that you want to use. You'll need to verify the email address.
7. Tap Settings > iCloud on your iOS device, and sign in with your new Apple ID. 

If these steps don’t work, change your Apple ID temporarily again. Then sign back in to My Apple ID to make sure that your Apple ID was changed.

 

If you're asked for the password to your previous Apple ID in iCloud - Apple Support

Take care,

Alex H.