Credit card settlement

I received an option to settle my credit card early November 2019 which I accepted, the installment was worked out over a period of six (6) months starting from November 2019, meaning that April 2020 would be the last installment. I have not missed any payments and I now receive an sms stating that there is still a balance owing? This same sms comes from a Mariette Horn, who in December sent me an email with another settlement offer and when I enquired about it, I was told "oh no sorry you already have one in place", I mean really, you are the manager and you don't know what's going on in your own department, as to who received settlement amounts etc? I would like confirmation that my payment has been received and that the account is now paid in full and closed. Thank you.