No Option for or help with a Refund

I purchased two business class fares to Japan and back and now Jetstar has cancelled the flights and can offer no alternative means of flying. I can get a refund of the fares on my insurance policy but I would need to get written confirmation from Jetstar that the credit they are offering is cancelled. I have no use for the credit of $4000 because I don't fly that much, especially with a budget airline like Jetstar. I just want a refund or help so that my insurance will pay.