Device installed stopped working in two months. Waiting 9months for Technician

After a few months of installation device stopped working December2023. Been calling customer care weekly and promised a technician will come. To date no one has come out. I have used every platform to contact you, customer care, email, whatsapp, live chat and receive same response. Now am here. I paid last installment in June, hoping to get some kind of response/assistance/movement from you and I received a call from your accounts department last month only that am in arrears. I explained my problem, being sent from pillar to post and was promised a technician would come same week, to date no one has come. Final straw is that we booked an appointment for new installation for a different car and a technician was scheduled in less than 48hrs because it's a new sale. We are on the 9th month of the year, i cannot believe that I haven't received any assistance from you. This is my last attempt, if my problem is not resolved, the 3 cars from my household will no longer be using your services. I have alerted my other family members and friends regarding my frustration. We will be taking our business elsewhere. I cannot be struggling this much just for a mere device to be fixed/maintained/replaced, how much more should the worst occur...