Not realy. A minor can only void a contract while they are still under the age of maturity (again, usually 18), or for a reasonable time after they have reached that age. If a person does nothing to disaffirm the contract after they stop being a minor, the law can find that they will no longer be able to void the contract
This is why the debt is now listed on your credit report, the contract is valid. If you can prove that you provided proof to the creditor that you were indeed a minor, then they are the ones that have violated the law by accepting the contract. This could be your evidence to have the item removed from your credit report.
If you have this evidence, then submit a written request to have the item removed from your report. Be sure to include any supporting documentation.
Here is a link on how to dispute with the CRA's
http://www.ftc.gov/bcp/menus/consumer/credit/reports.shtm
Download a pdf file regarding how to dispute with CRA's
LEGAL DISCLAIMER: The advice contained herein is for informational purposes only. It is not to be construed as Legal Counsel nor Legal Advice.