I recently received two letters stating that a new SIM card (attached to letter) needed to be inserted in our mobile phones, due to a network upgrade.
First I tried the SIM card in my phone - Nokia 100 and received the message SIM not valid. After many long and exhausting waits and phone conversations to Call Centres and actions such 'activating the SIM' performed and wait up to 24 hours, nothing has changed from 'SIM not valid'. (The unlock code is of no use, as upon presentation of SIM not valid message, no actions can be performed.
I tried the swap of SIM card on my wife's phone (Nokia 1101) and encountered the exact same error - SIM not valid..
Reading this forum, I note some people have purchased a different make of phone, in order for the SIM card to work. But we have been perfectly happy with our Nokia phones and don't understand why it should be necessary to take this action, when I assume the fault apparently lies with Virgin and the set-up up of their SIM cards with 'old' Nokia phones.
Having never seen or used the forum before, I thought if I logged my fault, then somebody from the 'Forum Team' would be able to assist, as I'd read they had come to the rescue for other customers who were having similar problems.
I spent a lot of time researching this (as I have a Nokia) and the problem is that most of the old Nokia phones have a software lock (meaning the software in the phone's processor chip) and this cannot be unlocked using a remote unlocking code. The only way to unlock affected Nokias is by downloading new software into the processor - basically reprogramming the phone. It means the new SIMs aren't compatible with the network locking method used by these older Nokias. Unfortunately if you have an affected Nokia, you won't be able to unlock it by typing a code into the handset.
This isn't a problem with Virgin's SIM set up, it is how Nokia set up their phones to hard-lock them to a network (VM used to use the EE network so that is what the phones got locked to). There is software out there on the internet, but it means connecting the phone (by cable) to a computer so you can download new processor software into it (there's also no guarantee it will work properly).