The phone call you have mentioned is certainly by Idea Cellular staff and not from Lok Adalat. Have you received any notice from Lok Adalat.
In Lok Adalat also both the parties make their representation.A Bill of Rs.1900/- can not become Rs.12000/.
Company shalll have to produce documnets in which you have given your consent to pay late fees and agreed amount if interest if any.
Have you received any bill showing dues of Rs.12000/-.
If you had lodged any complaints with the company complile them and make an issue, and settle the bill for less than Rs.1900/. Hope you have not supplied your PAN card copy, and it si not required to be submitted.
Obtain acceptance/settlemnet letter/NOC from company and a declaration that they shall be withdrawing the case from lok adalat and credit rating agency if any, submit a certified copy issued by them to you.