FTTP Upgrade for landline only service ?

Hello,

So the situation is, my grandparent (80) still has an active standalone landline service running FTTC

Allegedly in her area which is entirely FTTC but eligible for FTTP upgrade, FTTC has been a bit unstable for a while and I’ve heard multiple cases of frequent dropouts in her area

Also being fully aware that the FTTP upgrade does require a higher speed tier - but she also doesn’t require internet which would be a little over double what she is currently paying ($34)

Would ordering a service on a 4 Port NTD (on port 2) work to essentially force a FTTP upgrade so she can retain her existing grandfathered landline plan?

Or is there a way that an FTTP upgrade could potentially be done while retaining the plan? Or has the upgrade been done before while retaining a grandfathered landline only plan? It’s more for stability - she does have a mobile, but she also still gets a lot of calls through her landline so cutting the landline is not really an option