MTS Internet Services — extorting money in a mafai lfashio

well we have used mts data card for intenret services untill jan 2013, and before disconnecting their servcies we made a final payment of 530/- rupees, and in days we have received another bill for 192 rupees, we were confused and wroite for clarity on the bill to mts, which till date went un answered, all of a sudden in the last week of october 2013, we received a call from lawsolutions, a collection agency mts hires, threatening us in an extortion fasion, to make a payment fo 2500 or apppear in the court in delhi the next daym we made the payment and wrote to mts, which now plays hide and seek saying there is no account under the given account number by us.