Static IP for voip

[#1]

My parents have switched their Plusnet to broadband only, and their phone number has been ported to AAISP voip. Fine so far, but I want to have static IP on their Plusnet broadband to make the voip more reliable. I cannot find an option to enable static IP when logged in to their Plusnet account, where can I find it please?

[#2]

@OwenSmith  Plusnet no longer supply static IPs, they were discontinued about a year ago. Why do you think a static IP for VOIP is better? I have had a VOIP line for years most of the time with a dynamic IP address, it works for me.

[#3]

If the external IP address changes, the voip server won't be able to send an incoming call to my parents phone for up to 3 minutes which is how often it re-registers with the voip server. When it rains we get several line resyncs per hour due to the wires getting wet, and full fibre is not available where my parents live. Each resync changes the external IP address.

If I had known Plusnet no longer support static IP my parents might have changed ISP. They stayed with Plusnet because I knew from research I did at the end of 2024 that they supported static IP. It is very disappointing to now find out they no longer do, that change was not at all advertised. Now we're stuck with a new 2 year contract and no option to get static IP.