Still seeing ads after buying the pro version

The problem is that the free version and the pro version of the app can both be installed at the same time. After upgrading, you may still have the shortcut to the free version on your homescreen. On some devices the word free may get cut off and it isn't obvious which version you are opening.

To fix this, you can either uninstall the free version or remove the shortcut from your homescreen and add a new shortcut for the pro version.