• To dial from a land line phone in one area to another area a prefix of “0” is added to the STD number.• When we are dialing from a mobile phone in India to any landline even then we need to add “0” before the STD code irrespective of the area.• A code of four or more digits, other than those comprising a telephone number determines the routing of a call.• If dialing from outside India, a prefix of “+91” is required with the STD no. to connect a call.