Q: Can't get rid of old Apple ID

All content (apps, book, music, movies, etc...) are forever tied to the Apple ID used to obtain them.

Try here: https://iforgot.apple.com

Cristeu wrote:

 

I keep getting my old Apple ID on my phone and I don't remember the password even though I have now set up a new Apple ID I can't seem to have access to it because I can't remember old password - help anyone?

This old Apple ID that you are being prompted for, is it doing so when you attempt to update Apps? Are you seeing this email when you navigate to...

Settings>iCloud, iTunes & App Store, Facetime, Messages?  If you are seeing the same old account logged in anywhere, tap the Apple ID listed in blue and choose to sign out of it. You can then sign in with the appropriate account. For iCloud, you will need to know the login information to sign out at the bottom of its page. Did you simply update your Apple ID to a new email address? If you did, then use the same password that you are using for your present Apple ID (caps and #s) to sign out of iCloud Settings.

Apple recommends that you only have 1 Apple ID for all of your devices. All of your past purchases with iTunes are tethered to a single Apple ID. If you start up a completely new Apple ID, you will be starting fresh.  These things can get confusing to move around, so if you find yourself scratching your head, reach out to Apple for free and verify with them that you have the right account in place. If you did lose access to an entirely separate account, they can also help you retrieve it so you don't lose content. Contact Apple for support and service - Apple Support

As mentioned, if you forgot your old account you first need to set it up properly in https://iforgot.apple.com and then make changes to your new email address at https://appleid.apple.com

Once all that set, follow the steps here to avoid the old account popping up:

What to do after you change your Apple ID email address or password - Apple Support