Upgrade tariff: charge price difference and preserve current expiry date for prepaid services

We would like a feature enhancement for subscription/package upgrades for prepaid services.

When a client requests an upgrade to a higher service package before their current subscription expires, we would like the system to:

1. Allow the client to top up the difference amount required for the higher package.

2. Allow the ISP/operator to upgrade the client to the new package.

3. Carry forward the remaining subscription days from the current package to the upgraded package.

4. Maintain the existing subscription expiry date after the upgrade.

5. Complete the process without requiring:

   • Credit notes

   • Manual balance adjustments

   • Manual recalculation of subscription periods

Example

• A client is subscribed to a Basic package valid until 31 July.

• On 15 July, the client requests an upgrade to a Premium package.

• The client tops up the difference amount required for the higher package.

• The ISP upgrades the client to the Premium package.

• The system carries forward the remaining subscription days to the upgraded package, ensuring that the expiry date remains 31 July.

The objective is that a client can move to a higher package/service plan during an active subscription period by paying the difference amount, while the remaining validity is preserved and transferred to the upgraded package.