You have a contract which you signed to get the benefits that you required. Part of that contract is that you service the debt that is created, providing you the benefit.
If you reneg then the other party can sue you for your departure of the terms of agreement. I guess that is where you are at right now. If they commence civil proceedings against you, you have the ability to defend yourself... but it is advisable to consult an attorney. They will have been able to lodge a default against you with credit reporting companies and this will negatively affect your credit worthiness.
If they are successful in court with gaining a judgment against you then they can also have the Court enforce payment and asset seizure of your things. Any shortfall will allow them to file for your bankrupcy.
Get an attorney and never sign anything that you do not intend to honor. Sorry if I have hurt your feelings here... but you have an honest answer that just might save your life if you use the info to re-establish friendly terms with the other party that will allow you to renegotiate more favorable terms.
Good Luck.... Don't Let this ruin your life.