TL;DR
No — you can’t add your own funds to the Streaming Reward card. It can only be used for services that cost within the card’s balance.
Full Explanation
At this time, there’s no way to add your own money to your Streaming Reward card.
Here’s how it works:
The card can only be used with the balance already available on it.
You’ll need to choose streaming services that cost the same or less than that balance.
If a subscription costs more than the available balance, the payment will not go through.
We recommend checking your card balance before signing up for a new streaming service to avoid any issues.