It appears that the main problem you are having is NOT staying off the phone, and doing things verbally! STOP DOING THIS!!! Stay off the phone!!!
There is absolutely no reason to ever speak to any third party collector aka Bottomfeeder on the phone! None whatsoever. It will always just make things worse. DEMAND that all correspondence be in writing, even if only by email, so you have a record of what was communicated.
At this point, after 17 years, it makes no difference whether or not the bill was paid or not. That is no longer an issue, as the "statute of limitations" has run out, which means the "debt" is dead. It no longer exists in the eyes of the law, and could not be collected in any court, and they know this.
However, the law does not prevent them from attempting to collect.
FYI...the "burden of proof" is ALWAYS on the debt collector.
Knowledge is power. Get some.
Check out many of the other collections posts here on ROR to see the pattern of this sort of fraud, and also visit budhibbs.com for some education on debt collections.