If your mother was a phone-only customer with VM, she should have been given a VM hub for the new phone line but with the hub set up to provide landline only (no internet).
Her monthly costs should not have changed although there have been some past topics (some time ago if I recall correctly) where eager sales agents were trying to push a broadband sale off the back of the phone switchover (which should not be the case).
The VM tech should have made sure the line was working before leaving and, ideally, reconnected the existing equipment. Unfortunately, the skills, knowledge, abilities and interest level of VM techs seems to vary massively, as described in topics on here.
You should make some further enquiries with the provider of the care alarm system about future options or modifications to the call system. The phone connection on the back of the VM hub behaves like an ordinary telephone socket so should work OK with an emergency call system but it is dependent on the VM hub being online in order to dial out. If the hub was offline for any reason then the emergency call out may not happen when needed.
Emergency care line providers should be able to offer options for the call to go out via a mobile connection as well to ensure reliability.
All phone providers are moving to this phone-via-router arrangement so moving to BT may not necessarily help as you could very likely be offered a similar type of connection there (either now or in the near future).
https://www.futureofvoice.co.uk/
The VM forum team staff don't usually reply here in 'Tech Chatter'. Someone may move your topic over to 'Home Phone' where you should get a reply from a VM forum team member within a few days.
