Airtel — overcharging bill

Address: 560012

Airtel phone number: [protected]
Complaint for bill dated 6 Sept 2017.
I had activated International roaming plan of Rs 2999 for 10 days only once but when i received the bill on 6th Sept it was charged thrice. Then I immediately called customer care, they said that it will be waved off, but after calling many times to customer care only one waiver was given.
While charging the plan there was no intimation that it was auto-renewable plan. moreover while I was abroad there was no service for three days.
I stayed abroad for 12 days. So for two days 649 plan should be charged instead which company advertises.
Now company is calling my friends and family and giving threats that they will file a case against me and I will have problems in my passport and visa.