Harassment and theft attempts

Has anyone experienced harassment from these people ? It has been more than a month that they keep calling my number every morning at 7am. When you pick up the call, they drop the line. If you are lucky, the correspondant asks you when you are making the next payment. I have made numerous calls to advise that I have completed payment, provided proof of payment as requested more than 3 times, they even sent me an email advising they will forward a paid up letter. Nothing has been done yet they keep disturbing my sleep every morning including weekend. Their calls are recorded as we are told on every interaction, this can be easily investigated, and their WhatsApp correspondant has been ignoring my messages since May 29th