I paid so why am I being harrassed

I owed melomed gatesville a co payment of R250 last October and I paid it on November 19th. I am now receiving sms and statemenrs saying I still owe them.I confirmed last week payment was received it was paid in the incorrect account but the accounts lady would transfer the payment.so please tell me why am I still being harrassed for a payment I made 3 months ago