Filed by mail - but did not post it yet - realized I am a non-residential alien - can I do regular paper filing and opt out of Turbotax? Is my tax already filed?

I chose the file by mail option. Then I realized the form is incorrect since I am a non-residential alien. I haven't yet mailed the forms - can I opt out of Turbotax and file my own form taxes? Has Turbotax already sent my tax info to IRS? I am afraid.