Bank of America Settlement letter vs offer Question

I have a miracle in the works, but I need to know if it is valid.
I have a letter from a collection company that is handling
a debt for Bank of America. I am making 4 payments to this company.
The settlement is for one payment per month.

I have made 2 payments so far. The 3rd payment is due in 2 weeks.

HOWEVER, I just received a letter from Bank of America thanking me for the 2 payments and saying my debt was settled in FULL. It is a full blown settlement letter saying they will report it to the credit beaureus as SETTELED. I cannot believe it. It also has a name and a contact on the letter that I can call.

Does this settlement letter, which is for the SAME EXACT DEBT that I was paying on to the Collection Agency that was working for Bank of America, supercede the settlent offer I received from the Collection Agency?

To summarize
- I made 2 of 4 payments to the collection agency that was working for Bank of America
- I received a letter from Bank of America saying " Thank you for your final payment toward the settlement of $xx. This payment serves as the full settlement of the above - referenced account" etc.

If this does satisfy the debt, which I think it does, what should my next step be?
Will this settlement letter hold up in court? Or can B of A say it was a mistake?

I will leave full details of the amounts after I know what is happening.

Thanks