My filing status should be Single but it is show filing jointly.

Go back to the Personal Info section and make sure you did not indicate that you were Married- if you are married on December 31st you cannot file as Single.

Are you using an old account that was used for past joint returns?   If so, you should start a new account with a new user ID.  It is too hard and messy to remove the embedded "spouse" stuff from an account.

https://ttlc.intuit.com/community/using-turbotax/help/how-do-i-start-another-return-in-turbotax-online/00/25596