Even if you have no messages.
I just checked to see if there were any messages from a missed call I had. To be greeted with a nice bouncy message telling me they had "upgraded" my voicemail.
What does this mean? It means they completely wiped all saved messages I had, deleted my greeting and deleted my mailbox access pin.
This is NOT service. Had I gone to France and needed my mailbox it would not have been possible and I would have received a wonderful message telling me that once I returned to the UK I would be able to set my pin and access my messages. I also prefer that I'm asked for my pin even on my own phone. The reason being that if someone does, somehow, manage to clone my phone they still can't access my voicemail without trying to use the service desk to reset it.
I'm seriously not amused at their customer service levels of wipe and replace with default. However they will get away with it because my contract with BT is now impossible to get. I have a 366 day EU roaming contract which continues until I choose to "modify" or "renew" it. As I had moved it to a 60GB 5G contract before the split and because it is a family plan with that allowance per phone, not per plan and I can add or remove sims to the plan without modifying it, I have something it is impossible to get, works perfectly for Mrs S in France and is just enough data for me to use it for business or a bit of leisure without ever running out. So I won't be leaving them even if their service is to services what Josef Mengele was to medicine.