Open APIs

Hello, 

I have a doubt related to Recommendation API that someone may help me with. 

Let's imagine the following scenario:
- I have a customer that has 3 prepaid subscriptions and i want to get recommendations for one of the subscriptions.

Recommendation API allows me to pass the relatedParty.id of the customer, but i'm not able to pass the product.id of the subscription that i want to get recommendations.
Also, this API only returns recommendations related to a determinate customer? Is not possible to associate the recommendation to a specific subscription? 

I'm asking this because i can have a recommendation associated to a customer, that won't be eligible for the subscription that i want and the response will induce the user in error.

Thank you so much in advance.

Best Regards,