There are a few methods for this and will depend on whether you will need to update the quantity between now and the updated amount.
Fusebill has the ability to automatically uplift prices, either by a dollar amount or by a percentage. This works best if you have a consistent uplift pattern. It also automates the process if it naturally repeats, and can be visible in various reports. This is the preferred method.
Alternatively, a price override could be added to the customer as long as no quantity updates will be added to them. This works for a one time change on a specific subscription product. the challenge is that any quantity changes to that product may result in charges for the new pricing, depending on the related plan product pricing timing.