Show me how to cancel this – Encyclopædia Britannica Review

my son downloaded it years ago, and now we're getting monthly charges, and I cannot find out how to cancel this. firkin frustrating. Please let me know how to cancel this. it's not even on a phone we have anymore, yet i still am getting billed. for it. any help would be appreciated.
Review by pow_haaweeese on Encyclopædia Britannica.