Idea Cellular — Sim Card suddenly stop functioning.

Address:

Pune

Suddenly Sim Card stop functionating. When I reached to Service center they said there is a fault in my SIM Card, Please change it, and they charged me Rs 75/- for same.
Meantime 4-5 more customers came with same problem.
How come all the sim cards suddenly got faulty?
Even after sim card change the issue didn't resolved.
If the issue is from Service Provider, then how Service Center peoples are confidently telling to change the Sim and charging us Rs 75?