Changing apple id on iphone to match ipad.

Hello Rbbwatcher,

It sounds like you need to sign out of the Apple ID on your iPhone, so you can sign in to the one being used on your iPad.

To do this, you'll need to follow these related steps to sign out of your Apple ID on the iPhone: Sign out of iCloud on your iPhone, iPad, iPod touch, Apple TV, or Mac - Apple Support

Sign out of iCloud on your iPhone, iPad, iPod touch, Apple TV, or Mac

If you want to stop using iCloud on one of your devices, learn how to sign out and what happens when you sign out. 

What happens when you sign out of iCloud on your device

You can sign out of iCloud any time you like to stop using iCloud and its related services on your device. These services are listed below. Before signing out, make sure that you’re comfortable having these services turned off. If you only want to stop using some iCloud features, you can change your iCloud settings instead of signing out of iCloud. 

- Apple Pay, Apple Cash, and Apple Card*

- Find My

- Game Center

- Home app to control your HomeKit devices

- iCloud Backup

- iCloud Drive

- iCloud Keychain

- iCloud Mail

- iCloud Photos

- Siri Shortcuts

- Voice Memos

- Shared Albums

- Messages in iCloud

- Reminders

- Shared Notes

- Shared Pages, Numbers, and Keynote documents

- Updates to your contacts, calendars, reminders, bookmarks, and Safari tabs

- Continuity features like Handoff, Universal Clipboard, and Auto Unlock with your Apple Watch

- App data for any third-party apps that you've installed that use iCloud

When you sign out, any data stored in iCloud will be removed from your device but will remain in iCloud. Before you sign out, you’ll be asked if you want to keep a copy of any of this information on your device.

If you have iCloud+ and you sign out of iCloud on your device, you lose access to iCloud Private Relay, Hide My Email, HomeKit Secure Video support, and custom email domain** on that device. 

* Your Apple Cash and Apple Card accounts are linked to your Apple ID. They can't be transferred to a different Apple ID or accessed by a different Apple ID.

** Not all features are available in all countries or regions.

Sign out on your iPhone, iPad, or iPod touch

1. Go to Settings > [your name]. 

2. Scroll down to the bottom.

3. Tap Sign Out.

4. Enter your Apple ID password and tap Turn Off. Forgot your Apple ID password? 

5. Turn on the data that you want to keep a copy of on your device.

6. Tap Sign Out.

7. Tap Sign Out again to confirm that you want to sign out of iCloud.

After this, sign in to the other Apple ID you wish to use on the iPhone. Once you've done this, you can then set up text message forwarding, if you wish to receive your texts on the iPad: Forward SMS/MMS text messages from your iPhone to your Mac or iPad - Apple Support

Let us know if this helps out, take care.