you can do down to digicell store in city center and pick one up, they might be able to use your existing sim card but if not youy would need to buy one of those two. I would estimate for a simple phone about $30usd and about 10 if need simm card. YOur phone might not have totally died but if you have not topped off every 2-3 months they will inactivate your simm and you will have to buy another.

good luck