You have no right to break a lease unless you are a member of the military. When you do break a lease, a landlord has a duty to re-rent the property to mitigate his losses. You would be liable for the rent from the time that you vacated the property until it was re-rented.
The landlord/collection agency can do nothing unless and until they get a judgment against you. If that occurs, its like any other money judgment. The judgment becomes a lien on real property that you own. With a judgment, the creditor can levy (seize) bank account unless you exempt it. They can also seize and sell any non-exempt property that you own free and clear.
You need to think about resolving this issue. Also, you do not provide any dates so I cannot tell whether you have any viable defenses (like the statute of limitations).
Assuming that you wish to resolve this in a non-bankruptcy context, I can help for a reasonable fee. Please contact me at [email protected] if interested.