2Checkout gateway improvements
4 Must have changes on the 2Checkout gateway:
1. Cancel CC 2CO subscription once an WHMCS account is cancelled.
2CO currently provide facilities that can be used to cancel the recurring billing if a user's account is canceled within WHMCS. The Admin API call STOP_LINEITEM_RECURRING is used for this task.
2. Doing the same as #1, for users changing their plan from a paid to free plan.
3. If a user changes his plan (the paid amount changes) and he has a subscription the amount will be adjusted.It can be done by cancelling the old subscription and create a new one. Use Admin API call STOP_LINEITEM_RECURRING as well to stop the billing, then direct the user through the purchase process to create a new billing agreement for the new plan.
4. Identify duplicate payments / stop creation of more than one subscription.Use order details (client id, invoice id etc') to prevent the creation of a new subscription / payment / manual payment if a subscription already exist for this client.Also don't let overpay an invoice