Problem with apple ID

Try resetting the App Store:

Close the App Store completely from the app switcher window by double clicking the Home button and swiping up the App Store preview pane until it disappears from the screen. Then sign out of the iTunes Store (in Settings).

Then restart the device.

Then sign back into the iTunes Store and try downloading again.

Also to change the Apple ID go to the following locations under Settings, sign out of all of them and then sign back in:

iCloud, iTunes & App Store, Messages, FaceTime, and Game Center if you use it.

What you do after you change your Apple ID or password?

https://support.apple.com/en-us/HT204071

Any apps or music you purchased with your old Apple ID will be linked to that Apple ID. Did you create a whole new Apple ID or just edit the email address for your Apple ID?

If you created a whole new Apple ID, then you will need to delete any apps purchased with the old Apple ID and then download them again using the new Apple ID.

Or, if you don't want to delete the apps, you can reset the password for the old Apple ID and use the same password you use for the new Apple ID so you don't have to remember 2 different passwords.

If you forgot your Apple ID password - Apple Support

If you have trouble resetting your password for your old Apple ID, you will need to contact Apple.

Contact Apple for help with Apple ID account security - Apple Support

Glad to help!

There is not a way to cancel a purchase. You would need to complete the purchase and then request a refund if you no longer want it.

Get help with an item purchased from the iTunes Store, App Store, Mac App Store, or iBooks Store - Apple Support