AIRTEL
Type FREE and send it to 54321(tollfree)
>>>>>>>>>
send a blank sms to 59103(tollfree), u will receive ur mobile no. in a sms
>>>>>>>>>>>
dial *140*1600#
*400*2*1*10#
>>>>>>>>>>>
*121*9#
AIRCEL
dial *122*131#
>>>>>>>
*888#
DOCOMO
*1#, *580#
>>>>>>>>>
*124#
RELIANCE
*1#
>>>>>>>>>
*111#
IDEA
*1#
>>>>>>>>>>>>
*789#
>>>>>>>>>>>>
*100#
>>>>>>>>>>>
*131*1#
VODAFONE
*555#
>>>>>>>>>>>>>
*555*0#
>>>>>>>>>>>>>
*111*2#
LOOP
*222#
VIRGIN MOBILE
*1#
VIDEOCON
*1#