Thank you for providing a paid version (too many apps don't even allow that option), but I would suggest getting rid of the free version altogether as it cheapens your product and, quite honestly, the Android platform. It will merely bring "reviews" like the quoted.

This is not the sort of app that fits the free profile, and anyone unwilling to pay the token amount isn't a real user, and there is little to no chance you'll make any significant amount on the ads in it. Make this the trial version -- no ads -- with some sort of arbitrary limit.