A SIM/account should only get suspended if you haven't bought a membership plan for 6 or more months.
7.2 In addition to the circumstances set out in Section 7.1 above, we may suspend (i.e. bar), restrict or end the provision of the 48 Services (in total or in part) if you choose not to purchase top up credit or make a chargeable use in respect of your Account for a period of 6 months.
Is that what happened here?
In any case you'll almost certainly have to contact 48 support to get them to look into this and hopefully rectify matters.
See the links in my signature below.
