Basically the best plan for YOU is the plan that gives you the most for the least. So you should talk to your supplier, and ask them to give you a detailed report of your usage and which numbers you use the most, what hours etc. Then ask them to put together a plan that takes into account any discounts possible. For example if you talk mostly with three people, have these three numbers in a reduced fare. And look at the hours and ask to join a limited hourly plan if relevant.