My Mother received a purple sim upgrade many weeks ago. She has an old PAYG Nokia phone, so I bought her a unlocked, SIM free Doro 1360. I put the SIM in and its been working fine and her credit from the old SIM was transferred to the Doro. However, my mother is now getting texts saying "Urgent Action Required" and that call and texts will stop working on her phone. She has had another text today with a similar message and that another SIM is on its way and to use it or the phone will stop working.
What's going on? Do I have to put the latest SIM in her phone?