MTS / Sistema Shyam TeleServices [SSTL] — Threatening and misbehaving

Address:	New Delhi, Delhi, 110035
Website:	Www.Mtsindia.in

1. I bought this data card with Number [protected] 1 year later. At that time its speed was good and at the time of purchasing the card mts store manager told me that whenever i will surrender my device i will have 50% of its bill amount and now they are denying to pay.
2. From last two months i was facing speed issue for which i have complaint for that many times in store but not even a single time my complaint got registered.
Then on 28th of aug i used to call customer care and told complete story to executive and i requested him to diconnect my connection and i told him that u have to pay back 50% of my data card amount as promised at the time of purchase.
I wont pay any final amount u have to adjust it from my data card value and i can surrender my data card but i wont pay any amount.
Now their executive called me daily 2 or 3 times and use very harsh and abusing language and asking for final amount.
Kindly register a complaint against their misbehave and misguiding me.