API Subscription trying to change current subscription product

API Subscription trying to change current subscription product

I want to upgrade/downgrade existing subscription to another PRODUCT PLAN.

Example:
Currently USER is subscribed to PRODUCT “BASIC” and PLAN “Yearly”. I can switch PLANS (upgrade/downgrade) inside the same PRODUCT, that's fine.

But if I want to change USER PRODUCT PLAN from PRODUCT “BASIC” and PLAN “Yearly” to PRODUCT “PREMIUM” and PLAN “Yearly” I receive a ZOHO error saying CODE “107210” and MESSAGE “Specified plan is not allowed.“.

I tried with different product plans, monthly and early.

If this is not working, what is the flow that I should follow here?