Wrong and vast postpaid bill of mobile of idea

I have not paid my idea bill of 2000 Rs. and I have received a notice at my home. But as per bill I only talk  of 500 rs and  they charged me 1600 rs for internet uses which is within an hour.

So I have not paid the bill.and also i will paid the bill of 500 rs which is my real bill.

Other bill is very huge and rate is so high and the internet uses is very small.

Pl. advice me what should i do.