Hi,
As you can see on my profile page, I have experiences in building android apps that calculate used minutes of chatting apps like whatsapp, viber, etc.
The app name is WhatsAppStatistics, ViberStatistics, LineStatistics.
So, I can manage this project excellently.
I look forward to discuss with you.
Thanks.
Alex.
PS : If you want, I can give you apk file so that you can test my app on your phone.