Q: i changed my apple id but it did not automatically switch my iCloud id to match.  how do i change my iCloud user id?

Welcome to the Apple Community.

In order to change your Apple ID or password for your iCloud account on your iOS device, you need to delete the account from your iOS device first, then add it back using your updated details. (Settings > iCloud, scroll down and hit "Delete Account")

Providing you are simply updating your existing details and not changing to another account, when you delete your account, all the data that is synced with iCloud will also be deleted from the device (but not from iCloud), but will be synced back to your device when you login again.

In order to change your Apple ID or password for your iCloud account on your computer, you need to sign out of the account from your computer first, then sign back in using your updated details. (System Preferences > iCloud, click the sign out button)

In order to change your Apple ID or password for your iTunes account on your iOS device, you need to sign out from your iOS device first, then sign back in using your updated details. (Settings > iTunes & App store, scroll down and tap your ID)

If you are using iMessages or FaceTime, you will also need to log out and into your ID there too.

I am having the same issue with iCloud and apple id. I have tried to delete my iCloud account from my phone but it will not allow me to without entering a password to turn off "find my iphone feature" ... The problem is it is asking for my password for a user id that no longer exists.

The old user ID still exists as one can't delete a user ID entirely, just stop using it.  So entering the password for the old user ID should let you turn it off.

OT

Say my email used to be oldemail@bex.net and therefore my apple id was also oldemail@bex.net. My email then changed to newemail@gmail.com so I changed my apple id to newemail@gmail.com. When I purchase anything from iTunes/App store and it asks for my apple id and password it is under the newemail@gmail.com. However anything associated with iCloud is still coming up as oldemail@bex.net. I can't log into apple id under that old email address because it isn't registered as that anymore. I can't get my iPhone to change iCloud to the new email address, I also can't delete the iCloud account because it asks for the password for apple id account oldemail@bex.net... there is no password for that any longer....

I have the same exact issue. Have you figured it out??

I did! On your computer log into your apple id. Change your email address on your apple account back to your old one. Then (while you still have that open on your computer) log into your icloud account on your phone with that old email address. Now you can delete that account. Then on your computer change your email address back to the new one. You will have to veryify it in an email that they will send and then you can start a new icloud account on your phone with the new email address. Kind of a process but it worked!

I had the same problem also, what I did was Change my itune stores ID, then go back to icloud and turn off Find My Iphone with New Password even though it still show old ID - Then i was able to delete the ID then.