As always in case of "how to block ...... app" from accessing the internet, you visit your domain stats to identify the domains being used by the app and add this domain or domains to your "always block" list.
https://dashboard.opendns.com/stats/all/topdomains
Special candidates are everything with instagram.com or cdninstagram.com in it.
If you are not able to identify the domains, you refer to the author of the app to ask them, or you search the internet to possibly find these domains.
http://bfy.tw/HmJX
