There is a disputed debt clause in the fair debt collection practices act that says you have a 30 day window to dispute the debt in writing and request that the debt collector provide you more detailed information about the debt as well as documentation that proves that you are in fact the person that owes the money.
Until this information is provided by the debt collector they may not continue to seek payment from you and they are unable to take you to court over the debt. Because of this clause of the letter is written and sent the debt collector will have to cease communication until they have complied with the law.