If you never signed a credit agreement, then there is a case the debt could be cancelled out.
Also past payments with interest could be recovered.
I will seek more advice if i were you. Some of the earlier replies to you question, i would take with a pich of salt.
I have been in the same situation as yourself. You need to get as much advice as possible. If they do send you an agreement, do not sign anything.
If this case went to court, the judge would have to enforce the agreement.