I have just found a very useful excel utility to find a mobile number's provider and which city does it belongs to. This could be very useful to find a person's location immediately in case of misuse or to find where your missed call came from and can guess who that could or could have very many more uses. Just wanted to share it. It even works for reliance and tata indicom too.
You need to enter the first five numbers of the mobile number and will tell which city it belongs, who is the provider, and whether it is GSM or CDMA
You can download it here
2shared - download MOBILE_CODES_ONE_SHEETER_UPDATED.xls