Airtel — Threatening Calls and Harassment

My mother has xstream fiber ID [protected]. We took plan for only 6 months, but the plan continued even after that so I connected with call centre to cancel service but it was to be done from registered mobile number. As my mother couldn’t process the tedious process I called call centre, wrote email, generated complaints through app went to store (was assured service will be suspended) still the service has not stopped after 3 months. In these 3 months my mother (as it’s her registered mobile number) has received threatening calls on daily basis. On 27.01.2024, when I told the person that we will complaint in consumer forum we were further threatened to make payment. The amount is negligible but the harassment is completely unacceptable. Requesting support at the earliest.