1) telecom companies dont keep text and voice records for 4years
2) MTNL maintains Call detail records including inbound and outbound phone numbers and call duration (one year)
3) BSNL maintains IP session information - connection start end time, bytes in and out (three years offline)
MAC address of the modem/router/device (three years offline)
4) ex employee can use sms sent by you in court if he has not deleted that message . if he changed hand set records would not be available