When you upgrade your plan, you will be charged a prorated amount of the new plan. You will also be credited a prorated amount from the previous plan.
Monthly Plan: Feedback Central Basic = $25
Amount Due for Feedback Central Basic = $25
Switch on May 15 to: Feedback Central Deluxe = $50
Total Days of Basic Usage Left: 31 – 15 = 16 days
Amount Credited: $25 x (16/31) = $12.90
Total Days of Deluxe Usage: 31 – 16 = 15 days
Amount Due: $50 x (15/31) = $24.19
When you downgrade your plan, you will be billed at the new plan's rate starting next billing cycle. There will be no refund for the downgraded plan.