What you don't know is that by paying even a penny, the account is "Refreshed" and then they CAN sue, also they are very bad about "Settling" for (Say) Half, then passing along the NEW DEBT to another "Collector" so you pay again.
NEVER GIVE COLLECTORS A SINGLE CENT.
Also the above agreement to release you is NOT binding. It's just another LIE.
Plus NO ONE can remove anything from your credit report, the Credit Report Bureaus do not allow it, it's just a lie to get your money.