boardband device access is someone change

smart home manager is not work . also, billing cycle is something wrong too. sometime, modem lower light is red, but internet is working. for connect wireless i see only available Wi-Fi routers is that i used a long time ago and month. before, JUL/26th/2021 , new personal open DSL service with technician visit my home , but i found my website installed myself. AUG/05/2021 someone changed business acct and two more time visit my home with in a month. no one solved the issue. and there were more than 2 items that I didn't order. Even after all at&t calls, the same voice answered did no solve anything. also E mail sent to many time. but auto answer one time no more. because of these reasons, stop service and new open home DSL internet service last month. but more problems. i can't live normal life please help me thank you