They put the new SIM in and it still didn't work as the phone itself was now permanently locked. There was still the matter of why this had happened and then why several people I spoke to from two mobile phone companies didn't make that specific suggestion (except Vodafone shop, but for their own SIM) and why none of them knew what had happened or why to cause the problem. I still don't know. I ended up buying a new smart phone, a Galaxy J4+. I hope it isn't too tricky to learn to use.
