AWS Billing - EC2 - Compute saving

When you subscribe to AWS Savings Plans, how pricing works when changing instances depends on which type of plan you choose:

With Compute Savings Plans, you have the maximum flexibility. You commit to a specific dollar amount per hour (for 1 or 3 years), and this commitment applies automatically across:

• Any EC2 instance family
• Any instance size
• Any region
• Any operating system or tenancy
• Even AWS Fargate and Lambda

This means you can freely upgrade, downgrade, or change your instances without any manual intervention, and your savings will automatically apply to your new configuration. The system continuously evaluates your usage and applies the discounted rates to maximize your savings (up to 66% compared to On-Demand pricing).

With EC2 Instance Savings Plans, you have less flexibility. Your commitment is tied to a specific EC2 instance family in a specific region. You can still change instance size, operating system, and tenancy within that family and region, but you cannot change the instance family or region without purchasing a new plan.

In contrast, Reserved Instances require more manual management. Standard RIs are locked to specific configurations, while Convertible RIs allow changes but require manual exchanges, which could potentially cause administrative overhead.

The savings from your Savings Plans are applied immediately after purchase, and you'll see the cost differences reflected in your billing right away, unlike some other reservation models that might start at the next billing cycle.
Sources
EC2 Instance Savings Plan VS Flexible reserved instance | AWS re:Post
EC2 Instance Savings Plans | AWS re:Post
Pricing Of EC2 Instances: Saving Plan and Reserved Instances | AWS re:Post

I think you can't upgrade or alter your Savings Plan's commitment. For increased usage or new instance needs, you simply run them and either the plan covers them (if within limits), or you pay on-demand or purchase additional savings to cover the excess.

I am also having issue with pricing.