I've had a similar message from another number, I didn't stay on the line long enough to hear the full message though. They'll try anything to get your details I think ? Cheers

“This is X from the national broadband network, we have been trying to get in touch with you. However we are going to disconnect your landline and internet connection within 24 hours as the NBN is now available within your locality. For uninterrupted services please press 1 to get your self connected to a technician.”