Kiama residents have three months before their phones are cut off - if they are still dependent on the copper network.
Telstra area general manager Pamela Georgiou said copper-based phone and internet services would be wound down in parts of Kiama from May 23.
That meant that residents had 90 days to switch to the National Broadband Network service.
"It's important for people to be aware that the changeover isn't automatic and customers need to place an order to move to the NBN," Ms Georgiou said.
"We're encouraging any last-remaining customers to place an order with us by March 28. That way they avoid the last-minute rush and any potential disruption to their landline service.
"The reality is, customers in areas serviced by NBN's fixed-line network need to sign up to a voice service on the NBN if they want to keep their landline," Ms Georgiou said.