In most of downloadable software products there are no exceptions of paybacks for the purchasing.

If the purchasing is made by an Apple device:

Purchasing which being made an iOS device, Genetic Studios cannot make an direct process. Please visit Apple Support and first reach "iTunes Store Support" link, and then "Account and Billing" link to choose the fitting choice.

if the purchasing is mad by a Google device:

Please send an email to adress or get to the Settings > Help and Support section click the button "Contact Us" to contact us directly. Please insert a copy of the bill which belongs to the purchasing and mention the game the purchasing is being made. The Process Identity must be seen down below (GPA.1234-1234-1234-12345).

It would be beneficial to check this Article before you send an email.