There are multiple threads, throughout this community that discuss how to turn off the two-step verification. You can use the Search bar at the top of any page, here in the community, to find answers to most questions.
But to answer your question, this time, follow the steps below.
Two-step verification is a setting in QuickBooks Online where you need to verify, using a code sent to your mobile phone, that you're the one accessing your account.
If you don't need this setting, we can follow the suggested steps that were shared by Just_me to disable it.
The steps above are intended if you're still using the same phone number. If not, you'll need to update your contact information so you can sign in to your account. Once it’s updated, you can then turn off two-step verification. Here's how:
Complete the Email Change Request form. Make sure to enter your new phone number in the Recovery Number field.
Attach a copy of any of your photo ID forms. Then, select Browse.
Find and select the file, then click Open.
Once the file is uploaded, select Submit.
Once you receive a notification that your phone number is updated, sign in to your Intuit account.