How to remove my previous account from my App Store purchase

Apps are permanently associated with the account used to purchase them. If you are trying to update an app purchased with a different account then you have to purchase it again with the new account.

This may have been the result of incorrectly trying to change the email address you use with an account. Try to go back to using the old account by correctly changing the address used with it. However, you won't be able to use the email address you just used to set up the new account.

Here's how you change the email address (Apple ID) you use for your Apple Account while retaining everything in your account:

1. Go to https://appleid.apple.com and sign in.

2. In the Sign-In and Security section, choose Apple ID.

3. Enter the email address that you want to use as your Apple ID.

4. Choose Change Apple ID.

5. If you changed your Apple ID to a third-party email address, check your email for a verification code, then enter the code. Learn what to do if you didn't get the email. --> If you didn't receive your verification or reset email - Apple Support

6. If you use services like iCloud or Messages to share with friends and colleagues, sign in to those services with your updated Apple ID. --> What to do after you change your Apple ID or password - Apple Support

For more details, read the document: "Change your Apple ID" --> Change your Apple ID - Apple Support