As per I know once your app is in production, you cannot change anything.
You need to ask devsupport@ringcentral.com for any help. Once they added the permission with your request (not sure if they do.. most probably they don't) you need to test again for that permission you acquired.
The official recommendation is to create a new app, add proper permissions and graduate it. So in that case you need to go through again.
As per the reference here
"You can clone the app, give it a new name or add a version to the new app name. Add the missing permissions and run test in the sandbox the same way as you did for the first app. Graduate your app and finally replace the client Id and secrete to use the new app. You can suspend the old app after that."
Similar question here: https://forums.developers.ringcentral.com/questions/1059/how-to-add-permissions-of-read-call-log-in-product.html