Pathetic company

Absolutely pathetic company. My mom paid off her account in December 2020 already but she still gets calls stating she owes them money. She is 79 years old and has dementia and every time I answer the phone the consultants refuse to speak to me even though I explain the situation every time. They insist they want to speak to my mom. I have a letter stating my mom's account has a zero balance but they are unconcerned and still keep on calling with threatening messages. Really *********** and unprofessional.