Optus has announced end of life of their 2G network.
"The company announced on Wednesday it would shut down its 22-year-old 2G GSM network on April 1, 2017 - just over 600 days from now."
From www .watoday.com.au/ digital-life/mobiles/optus-sets-date-to-switch-off-2g-network-20150805-girw2e.html