Medical alarms and emergency call services connected to the copper phone line may not continue to work after the 18-month NBN transfer window has closed. Firstly, you should register your alarm at nbn.com.au/medicalregister or by calling 1800 227 300 well before the cut-off date. Then call your emergency or alarm service provider and check if it will work on the NBN; and finally, tell your ISP if you need priority assistance service levels.