After you file

You cannot change it at least not on TurboTax.  I guess if you use the wrong tax form when preparing by hand you could use a 1040.   I cannot think of a good reason why you would even want to.  A 1040A is a completely valid tax return form.
**Disclaimer: Every effort has been made to offer the most correct information possible. The poster disclaims any legal responsibility for the accuracy of the information that is contained in this post.**