I change my phone numebre, in orderr to cahnge they are sending a code to the old numebr wicht doesnt works any more how i suoppoet to change it?

I'm happy to see you here in the Community, @the-molinas.

I'd like to ensure that you'll be able to change the phone number on your QuickBooks Online account.

When changing a phone number for your QuickBooks Online account, a code will be sent to the new number that you've entered.

Here's how it works:

1. Go to the Gear icon at the top.
2. Tap on on User Profile.
3. Select on Security.
4. Choose Edit in the Phone section, then press on Change next to the phone number.
5. Enter the new number and the password.
6. Hit on Save.
7. Select how you want to confirm your contact information by selecting the following: Text message or Voice call, then choose Continue.
8. Confirm by entering the code, then tick on Done.

However, if the problem continues, I recommend accessing your account using a private window and update the phone number from there. The cache is in place to store older data to make loading web pages easier. If it gets too full, it can actually have an adverse effect and cause issue like the one that you've experienced.

If it works fine, you can go back to your regular browser and clear its cache. This will refresh the program and get everything back to normal. 

Other the other hand, if you're modifying the phone number for your payroll account, please follow the steps found in this link: Change email, password, phone number, or User ID for Full Service Payroll.

Let me know if you have any other concerns with this or with QBO. I'm always here to help. Have a lovely day!