Hi, thanks for those who viewed my message. I added it while I was waiting in the phone queue.
I persevered in the phone queue and finally an agent picked up. He took some details but could not help and put me through to a "technical" person, Andy. He said the new SIM card is not compatible with the Nokia 2310 and has ordered a new phone to be delivered by Monday at zero cost.
It took an hour waiting in the phone queue and another 30 minutes once through speaking to the helplines but hopefully, once the new phone arrives, problem solved.