CACH LLC Paid a debt with cach LLC and now my credit report still has me delinquent. Denver Colorado

When i got home from my second tour from the middle east with the navy i went through my mail when i got back home, i noticed a letter from a CACH LLC. I opened the letter and read it and it stated that i owe them an x amount of money to settle a debt with them, so i called the number and talked to someone that works there. I explained my situation to them and believe it or not they were kinda nice and they said they understood, i was told what to do and i told them that i would pay the amount they were asking for.

I sent them the payment with a certified letter and check, that they agreed to in advance to do and they told me after 30 days they would report it to all three credit bureaus. Now i just checked my credit report and they have me down as delinquent still and they never reported me paying them in full as they agreed on to the credit bureaus in my letter and while on the phone with them.

Is there something i can do? I have all my certified checks and letters that i sent them.

Thank you,
David S.
Corona, California
U.S.A.