I had the same SIM not valid problem on an emergency PAYG Nokia 1616 I bought for my sister about 9 years ago. After much abortive searching of the Virgin Mobile and Media sites with conflicting information, trying the Switch txt that didn’t work, I finally came to this Forum.
As the unblocking code was printed on the letter with the new SIM, I wonder why Virgin didn’t complete the information on how to enter it into the phone.
Having followed the #pw+code+7# process the phone now works.
At the very worst, instead of the unhelpful info on the Virgin website, they could have said that old phones would, probably need unlocking.
Brilliant! I have been trying to get the new SIM to work in my old Nokia 1112 - no success from VirginMedia helpline - they offered to send a new phone (Energiser E12) but it never arrived. Very grateful for this info how to input the unlock code and to get the old Nokia to work again!
Wish I had read this thread weeks ago.....have a Nokia 1100 and managed to spend nearly two days organising a new sim for it as I never received a replacement to start with...then my other phone managed to get disconnected and couldnt be restored...After another day of messaging got the credit for the other sim merged with new sim only to discover it doesnt work at all on my Nokia. Hopefully I will still be able salvage some calls in another unlocked phone but this saga has just become unbelievable!!! Although some VM elves are doing their best to help there are customers going around with hats on...not because of the cold but to to cover their hair loss over this!!!!!!! Surely it could have been made clear from the outset that the new sims may not be compatible with some old phones...with a proper database showing which phones would cause problems. Comiserations to everyone else who has had their time wasted.