Hi, thanks for quick reply.
"On 22 August your current home phone service will stop working and be switched over to our fibre network. We will send you an adapter in the post which you’ll need to use to connect your home phone to your WiFi Hub so you can make and receive phone calls over our fibre network."
Alarm provider said existing system is hardwired into traditional phone line and not possible to adapt without signficant hardware changes.