Hathway — Stop calling to renew account

Have disconnected the hathway broadband because of relocating to different part of chennai. I have called to customer care to stop the service but daily twice i'm getting call from hathway stating that we're providing offer please do recharge. How to stop this call? Do i need to come to your capital office and give you a written statement? As per your guidelines i reached customer care and informed to stop the service. What else expecting from consumer?