Just got Twitch Prime, subscribed to a channel and terminated the Twitch Prime subscription?

Did you pay for 0 Euro and get a free subscription to a Twitch channel?

Yes, with Twitch Prime, you get a free subscription every month, which does not automatically renew. So, even if the subscription should always get the same streamer, you have to subscribe again every month.

So I have not paid a cent for a subscription?

Canceled Amazon Prime and refunded the money back

No, there's a subscription every month for free.