Are you n00b in android development and uploading your first application?? Yes this error will surely come that com.phonegap package is already exist.
To remove this error..
Go to https://build.phonegap.com/
Before uploading your .zip code file, go to settings and type the package name as com.yourapplicationname or with standards it’s com.companyname.applicationname.
Now rebuild the your code. and upload your .apk file to google play.
Atleast this error won’t come.