Your sim card is possibly disabled because your phone is currently not activated or has not been used in over 3-6 months. You should go to your local service provider and have them check out the situation. You could just use a new one as the current sim card you have is ready to be replaced.
IT sounds like your phone company deactivated your card or more than likely someone tried to unlock it. Some phone will lock you out when you fail to unlock it.
My sim card is disabled due to network error. I have tried to enable it by calling call center but nothing happened. I need a sim card which has better quality and least expensive. Hopefully I will be getting the same hereafter what I had expected in the other operators.