What happens to my minutes/hours if I upgrade?

If you upgrade your plan, you'll have the full amount of the new plan plus any remaining hours from the old plan, and will be charged for the new plan. 

For example, if you use 1 hour of the 5-hour/mo plan, then upgrade to the 10-hour/mo plan, you'll have 14 hours for the rest of the month (5-1 hours from the 5-hour plan + 10 hours from the 10-hour plan), and will then have 10 hours each month after that.