Question Author
Thanks for those contact details dannyk13, I'll give it a try.
carrot99 I've no idea how to get the back off, there are no screws or clips etc.
(Wrinkly Rant: I still object to being pushed around by Corporate bodies, firstly the banks insisting on a mobile, then Virgin with this. It's cynical manipulation taking advantage of the Coronavirus situation where the mobile originally bought just for emergencies now becomes my lifeline)