You can update a membership category or any "product" from the Products tab of Manage clubs. However, it is important to note that this will not affect people who already own the subscription.
When a member buys (or is assigned) a product or subscription all the details are snap-shot and stored alongside the members record so that they are assured that what they paid for is what they will get for the duration of the product. So if a member buys a subscription that grants them off-peak court usage at, say, £5 per session - that price is locked in for the whole subscription period. If the terms of the subscription were changed to, say, £6 per court, then this would only apply to members buying the subscription anew. Existing subscribers would continue to pay £5 for the court.
You might think that this could add confusion if a court were booked by two people on different tariffs and the court fee has to be shared. But, in fact, there is no confusion as each player only sees their "side" of the charge. In the above example player A will be charged half of what they see as the court fee (£2.50) and player B will charged half of what they see as the court fee (£3.00). The net income to the club would be £5.50. The same logic would apply if, say, a Junior had a subscription that provided discounted court fees and who was playing an adult who did not.
However, a club official can override all this by specifically resetting any court fee charge on a subscription for every member who already has that subscription. To do so go to the CourtSets tab in Manage clubs and choose the court set that you have changed. You will see a list of all the products and events that use the court set. Against each is a record of the price set for the court set (they can be different for each product). If this price is different for any individual who owns the product then you will see a red button that shows a count of how many members differ. To re-align every members price to reflect the current price for the court set press the Re-apply button. A popup window will ask you to confirm this action.
The change will take immediate effect and any courts currently booked will be charged at the new rate as well as all future bookings.
You can also re-apply all updated details for a product as described in this article.