I told them I can pay when I cant

If you have never received a dunning letter (letter of collection) through the mail, you should NEVER admit to owing a debt to a voice on the phone, whether you owe it or not is irrelevant, a 3rd party collector is required by federal law (FDCPA) to send you a dunning letter via the mail, and are specifically supposed to do so within 5 days after they contact you.

I would tell them that you felt pressured into agreeing something you couldn't do and now, after having had time to think and to talk to your "sources" you must insist that they validate the debt before they go any further. Otherwise they will figure they have a live one on the hook and try to take everything from you.

Tell them if they got anything to say, PUT IT IN WRITING, don't call me.

You could also say you were flustered and thought they were talking about a completely different debt...you easily get flustered when CA's act unethical and browbeat payments out of you. ;) Send them a DV letter and inform them that there will be no more phone contact, that all correspondence is by mail only and that you want a full accounting of the alleged debt since they seem to be in such a hot rush for payment.