Frustrated client

I missed a payment due to unforeseen circumstances for this month, (my first time) I sent a number of emails explaining my situation and making arrangements for a double payment in January 2025 to which I finally received a reply from a Mr/Mrs Ntombi accepting my arrangements and saying that I must contact him/her if phone calls and emails continue as she has informed their call centre to not call me. Guess what, I receive a least two phone calls a day, and I explain to them each time what I have done. This is ignored, and I still receive phone calls and emails. The WhatsApp number does not work either. Please stop harassing me Nimble