no response regarding my paid up letter

I received a letter from this attorneys that i am owing doctor de wet from netcare an amount of 460. And the the lawyers admin fees of 463. I paid up the doctor on December already but the lawyers said I owe them admin fees and they listed my name on ITC. Sonia called me and I told her I will pay on the 25th of march which I did and sent her the proof of payment. I made a follow up and she said she received the payment and she will send me the paid up letter once the money cleared. Until today I haven't received that letter. I have been sending her emails to send me the letter and she is not responding to my emails. When I was still owing then she will send me emails left right and centre. Now that I have paid she is not responding to my email. Am just wondering if this lawyers aren't one of those ****s going around. All I wasnt is my paid up letter coz my name is on ITC for an account that was paid up already.