Capital One Settlement Letter & Windsor Group

I have been behind in my car payments for almost 7 months now and currently my account is being charged off with Capital One Auto Finance. I have been hiding the car because I believe as long as it is stay on my possession the negotiating part will be easier than when they already repos'ed it.

I was contacted today at work from Windsor Equity Group. Can't hide when they called at work (I wonder how I can stop this).

I responded and the guy told me there is no negotiation can be done until they have the car and inspect the car and forward condition report to capital one. At that point capital one will tell me if they want to reinstate the loan. I had no choice but willing to surrender the vehicle.

I took one last shot calling Capital One Office in VA because it is the only number that will not transfer me to Windsor Group. I spoke to someone and she willing the settle 20% off the total I owed. I agreed and right now gathering money and sell stuff that I can afford to sell.

Here is the problem:

- The letter stated that I have 10 days to accept the offer and the guy from windsor expected me to pay within 1 day or else he will contact capital one to reconsider the offer.
- The reason they expected 1 day because I was begging for the settlement and I told them that I can have the funds ready within 1 day (I didn't know people who lend me the money are in personal checks which need to be clear from the bank).

- The person from Windsor is giving me hard time. He is telling me that I didn't keep my word there for he will talk to capital one to reconsider the offer.

WHAT SHOULD I DO NOW-- PLEASE HELP!:(

Edit: I'm still in possession of the vehicle. CapitalOne person told me that there is no reason that I am sending the check and surrender the car at the same time.