Business Directory issues

I have never encountered such blatant disregard of customer service ever. A family member paid for services relating to what they do in 2019. But said family member died. He passed away. In 2020. BDM keeps sending letters to say money is outstanding and needs to be paid. I have sent his death certificate 10 times already as proof that he died. They keep sending emails. When I try to phone they refuse to answer but now they send messages to my personal nr to try and collect the money. So they refuse to speak to me but they can send an sms. How does that work? My cell nr has never been used in my brothers business. I am unable to get this sorted and now will be reverting to blocking them.