old phone and new phone still interconnected

I am not what this inter-connected means by you..

 If the data transfer process wasn't completed correctly, residual data or settings might be causing conflicts. Try using Apple's recommended data transfer methods like Quick Start or iCloud backup and restore to ensure a clean transfer.

You may try some of these steps, please check after each step...

1. Sometimes, a simple restart can resolve temporary software glitches. Turn off your iPhone, wait for a few seconds, and then turn it back on.
   1. Restart the device. That's it.
   2. Still not solved --> Force restart iPhone - Apple Support
2. Check iCloud Settings:
   1. On both devices, go to "Settings" > [your name] > "Find My" and make sure that "Find My iPhone" is enabled on both devices.
   2. Verify that both devices are signed in with the correct Apple ID.
3. Ensure that both devices are syncing properly with iCloud. You can check this by going to "Settings" > [your name] > "iCloud" and confirming that all necessary data is being synced.
4. On both devices, go to "Settings" > "Notifications" and ensure that notifications are set up correctly for each app.
5. Double-check that both devices are using the correct iCloud account. Go to "Settings" > [your name] > "Sign Out" and then sign in again with the correct Apple ID.
6. If the issue persists, you can try resetting all settings on your iPhone. This will not erase your data but will reset all personalized settings to their default values. Go to Settings > General > Transfer & Reset > Reset > Reset All Settings and confirm the action. Note that you will need to reconfigure your settings afterward. All settings—including network settings, the keyboard dictionary, the Home screen layout, location settings, privacy settings, and Apple Pay cards—are removed or reset to their defaults. No data or media are deleted.
   1. Reset All Settings: Return iPhone settings to their defaults - Apple Support:- Return iPhone settings to their defaults
   2. You can return settings to their defaults without erasing your content.
   3. If you want to save your settings, back up your iPhone before returning them to their defaults. For example, if you’re trying to solve a problem but returning settings to their defaults doesn’t help, you might want to restore your previous settings from a backup.
   4. 
7. Make sure you have the latest updates installed.
   1. Update Over-the-Air (OTA) —> Update your iPhone or iPad - Apple Support (IN)
   2. Update using iTunes/Finder —> Update your iPhone, iPad, or iPod touch - Apple Support (IN)

Solutions to Try:

• Double-check data transfer: Ensure a complete and clean data transfer using recommended methods.
• Verify Apple ID and iCloud: Use separate Apple IDs and review iCloud Keychain settings.
• Adjust app notification settings: Configure notifications per device within each app.
• Consider new backup: Start fresh with a new backup dedicated to your new phone.
• Update iOS: Ensure both iPhones run the latest iOS versions.

If none of the above steps resolve the issue, it is recommended to reach out to Apple Support or visit an authorized service center for further assistance. They can provide specific guidance based on your device model and iOS version.