Hi.
Closed Testing is a pain in the neck but its required by Google.
Especially for paid apps during that testing stage. Testers will be charged, whether or not you like it. My app went through the same procedure about 3 months ago.
But there is a backdoor for developers in order to get you through that phase without testers having to pay:
Set your paid app to € 0,00 temporarily (let's say 2 weeks). During that time testers can download and test your app for free.