In-App Purchase does not work

I downloaded the free version of this application to view a DAT file, which worked perfectly. However, I then purchased the in-app purchase (upgrade to PRO) so that I coul view a PDF attachment inside the DAT file. After purchaing the in-app upgrade, I was never able to access the attachment. I was only repeatedly asked to upgrade over and over again. I did attempt to restart, reinstall, and even repurchase the upgrade several times, but without any success. I will be contcting Apple for a refund of the in-app purchase as I currently consider it to be a fraudulent sale on the part of the developer.

Bmicallef about Winmail.dat File Viewer