Fidelity ADT Security

How bad and very unprofessional. I have canceled my contract with Fidelity ADT beginning of 2023 and every month they send me notice of an outstanding balance. Just to send SMS to say ignore. Then to receive a telephone call from LGR Attorneys to say I owe ADT money. Then to receive an sms to say "Dear customer kindly ignore the SMS received from LGR yesterday. When phoning in, ADT ask me to send them the correspondence as they do not have it in the file. Really????