jabber pop up won't stop popping

Hello and welcome to Apple Support Communities, beverlyfromriverview.
If I understand your post correctly, you are using a Jabber account in Messages on your Mac and you'd like to receive fewer notifications from Jabber. I'd like to help.
To manage the notifications for Jabber, click the Apple Menu () > System Preferences > Notifications and locate Messages in the list on the left. Once you click on Messages, you'll be able to select how you are notified about new messages.
For more information, check out this article:
Change settings in System Preferences
If you'd like to remove the Jabber account completely, follow these steps:

Stop using an account

If you don’t want to see messages from an account on your Mac, you can make the account inactive using Messages preferences, or turn off or remove the account using Internet Accounts preferences.

Do one of the following:

• Make an account inactive: Choose Messages > Preferences, click Accounts, select the account on the left, then deselect “Enable this account.” When you make an account inactive, your status is displayed as Offline.

• Turn off Messages for an account: Choose Apple menu > System Preferences, click Internet Accounts, select the account you want to stop using for Messages, then deselect Messages on the right.

• Remove an account from your Mac: Choose Apple menu > System Preferences, click Internet Accounts, select the account you want to stop using, then click the Remove button .

WARNING: Deleting an account or turning off individual features can remove data stored in your apps. Before the account is deleted or a feature is turned off, you’re asked whether you want to keep a copy of the data.

See the full article here:
Messages for Mac: Set up other Internet accounts in Messages
Let us know if that resolves this issue for you.
Thanks for using the Apple Support Communities. Take care.