Can we change the phone number for a quickbooks user that is setup?

The user must be the one to update the phone number associated to the account, @slsBetty.

They can go to the Intuit Account Manager to update the phone number associated to the account. 

You can provide to the user this Intuit Account Manager link and let them go to the Sign in and security menu.

Follow the steps below:

1. Let them use their QuickBooks log-in credentials upon logging in to the Intuit Account Manager
2. Click the Sign in and security from the left menu and click Phone. 
3. Update the phone number and click Save once done.  

You can check this article for more information: Change your email, user ID, or password for QuickBooks Online and QuickBooks Self-Employed.

Once done, you can let them login to the account. You can also provide to the user this article for more information: What to do when you are locked out of your account.

Let me know if you still have questions and or anything else. I'm always here  ready to help. Have a wonderful day!