A person who had my phone number before me has an account. I'm worried if someone attempts to use that phone number they will gain access to my account as well.

[Cynthiad66]

No.  Establishing an account requires more than a phone number.  The phone number is usually used to verify access.  

[DoninGA]

To access your online tax returns only someone who has the User ID and Password for the account can access the returns, not just a phone number.

You can change your TurboTax account information at any time.

See this TurboTax support FAQ for updating your account information - https://ttlc.intuit.com/turbotax-support/en-us/help-article/account-status/update-turbotax-account-i...