The girl had breathed her last on Saturday in a Singapore hospital.
Senior Delhi government officials said the helpline could not be made functional due to some glitches in the MTNL network.
They said the helpline, which will operate from the chief minister's office in Delhi Secretariat, can be contacted from landlines as well as mobile phones.
The telecom ministry had last week released the three-digit number following a request by Dikshit. It will be the first three-digit number to have been allotted by the ministry in two years.
The ministry had earlier allotted 167 for the helpline but upon request for a number that would be easier to remember, the number was changed to 181.