I have a hutch pre-paid connection

Sir
I have a hutch pre-paid connection since 2004 In August 2006 I converted it to Post paid. Since last month my SIM is not working properly. I talked to customer care and got advice to visit Branch sec-18, Noida (U.P.)
He asked 250/- will be debited for change of sim charge.
Can i know within one month how the sim can be damaged while i donot used to open my mobile. I hope i was given old Sim.
regards
Ranjit Goswami