Question on Dispute

I am helping my boyfriend clean up his credit and we have addressed all the outstanding ones that showed up 7 years back.
We had a collection agency contact us about a debt that was from 14 years ago which we are going to dispute. I am unfamilar with this process can you tell me the things to be aware of.  I know we have 30 days to dispute, and we Can dispute as many times as we want.  Is a lower amount offered?

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You can always negotiate if the debt is verified

So yes Dispute