Wrong billing to the name of downloading charges

On 14th Oct,14 at night I talked to the Idea Costomer care between 9:51 to 10:17 and changed the packs of my iplan and next morning I found that my unbilled amount has been increased by around Rs. 525 though I didn’t use any of the service (either phone call or internets).
And when I talked to the customer care again, they told me that this amount was charged for the data usage on last night at 9:59. Here I would like to highlight the point again that at that time I was talking to the customer care to reorganize my plan so how can it’s possible to use data.

I complained many times and each time they said that they can help me only when the bill will be generated.

Now my billed has been generated and they has bared my service due to excess uses over my credit limit of Rs 100.
You are requested to please take suitable action against them soonest because I can’t afford to pay the said amount charged to me.