The package name is already in use for another application.

All of a sudden when I try send in updates to my release channel I get this.

The package name is already in use for another application. Every application must have a unique package name.

I thought we were supposed to keep the same information on the APK each release. My app is already in the store and I didn't change anything on the apk. Just the build number and version. I can't afford to delete this app and make another one. It is getting downloads and customers. Please can somebody help