As Julie says, you do have VoIP, and when properly implemented it should be indistinguishable from a traditional POTS line. It's how all "landlines" will be delivered in the not too distant future.
ThePillenwerfer's solution uses the bell-set's internal capacitor and should get you going.
The alternative is to use one of these:
https://www.amazon.co.uk/RJ11-teleph.../dp/B00DK2PG86
I don't know if you have an RJ11 plug on your linecord, or a normal British type of phone plug, and VM provided you with an adaptor. It may
look like the one in the above URL, but it probably does not contain a ringing capacitor. They can get away with that on 9 out of 10 occasions because modern phones generally do not require an external capacitor (which is located in the master socket of a traditional wiring scheme)