It is possible to switch from a Chapter 13 bankruptcy to a Chapter 7 bankruptcy. Switching from one chapter to another is called converting.
You can convert your case from a Chapter 13 to a Chapter 7 so long as you are eligible for a discharge. The discharge is what you receive from the court at the end of your bankruptcy case. You should discuss with your attorney whether it is in your best interest to convert.
It is also possible to convert a case from a Chapter 7 to a Chapter 13 bankruptcy case.
In a rare case here in New Jersey, the Court made a Chapter 7 debtor convert his case from a Chapter 7 case to a Chapter 13 case because the debtor received a really high paying job shortly after filing his case. The Court ruled that debtor could then afford to pay something back.