Balance owed on CLOSED Account

June 2014 I was contacted and an arrangement was made to settle an outstanding balance. I also asked the caller to update my last name, because it has since changed. I was advised no, because the acc is CLOSED and cannot be used again. Final agreed payment was made 9 June 14. It's now August 2018 and I'm being harassed, an apparent outstanding balance has to be paid, because I did not close the acc. I was not told to call back to close the account, because the account was already CLOSED when they contacted me initially to make the final payment. I'm growing increasingly tired of having this conversation on a near daily basis. I paid what I was told to pay. I was advised the acc was already closed. Please stop testing my patience. Go back, listen to your calls, clear the balance that has grown since I had settled and please stop contacting me, because if you tell me one more time that I owe money on a "closed" credit card you will not be please with my tone.