Your SIM gets suspended if you haven't bought a new membership plan for 6 months or more.
After that you have another c. 6 months before the SIM and account gets completely disconnected/deleted.
See the terms & conditions:
7.3 Where the 48 Services are suspended because you have chosen not to purchase top up credit or make a chargeable use in respect of your Account for a period of 6 months, we will remove any credit on your Account after a further 2 months and credit will not be recoverable. Your service will then remain suspended for a further 5 months and can be reconnected at any time during this period. When the suspension period ends your service will be disconnected, this agreement will end and your number will be immediately lost.
You need to contact 48 support to see if they can remove the suspension so that you can continue to use your existing SIM/account or if you need to start from scratch.
See the links in my signature below.
