Call from Delhi threatening legal Notice & Harassement call from Tata Docomo

Location/place: PUNE

Name of company/service: Tata Docomo (PHOTON)

Hi,
I had a Tata Docomo photon number 9225309737 which I used in the year 2012. firstly I activated giving six month advance rental plan & paid the amount, at end of six month they called & given new plan of six month advance rental, but without information/confirmation they activated plan of @Rs.1700/- per month rental & disconnected my connection @20days. After disconnection subsequently next month they activated plan for six month. I informed at their call center, collection boys & company showroom about cancellation of bill @Rs.1700/- & giving me correct bill for six month advance rental, so I can continue the service, but they have not corrected the bills nor given any proper response. Although they have sent their collection representatives for the payment collection, I informed them you kindly cancel wrong activated @Rs.1700/- bill & active my 6 month advance rental plan & give me correct bill/statment. But neither collection boy nor customer care responded. But keep on calling for collection of payment of wrong generated bills.
Today I received a call from this number 918459117543. There are Harassing me for the payment & continuously threatening for Delhi Police legal Notice.
I have been very badly humiliated and distracted from my work. I want Tata to pay for the humiliation and the bad conduct these people have.