Adding a Product

Use the Amendment object to add a product to a subscription.

To add a product to a subscription,

Create a new Amendment.
Set the Type to NewProduct.
Specify the subscription's ID.
Set the Type to Draft. Setting it to Draft is important because the amendment then won't go through until you insert the final part of the code.
Insert the new amendment.
Now create a new RatePlan.
Set the new RatePlan.setAmendment to the new amendment you've created.
Set the Type to NewProduct.
Insert the new RatePlan.
RatePlanCharges will be created in the background; for more information, see RatePlanCharge.
Set the following fields:

Set Status of the new amendment to Completed.
Set the ContractEffectiveDate to a date and time in the future.
If you have set Require Customer Acceptance of Orders? on your Admin "Default Subscription Settings" page to Yes, then you will also need to specify a customer acceptance date.
If you have set Require Service Activation? on your Admin "Default Subscription Settings" page to Yes, then you will also need to specify a service activation date.