Generally, all charges for in app purchases are nonrefundable, and there are no refunds or credits for partially used periods.  

Unfortunately, The Dyrt can’t issue a refund for any payments made after your free trial ends. 

For free trial period users, the trial begins before you are charged, so there are no payments to be refunded if you are still in your trial period. You can cancel your free trial any time during the trial period within your app’s subscription settings. 

Once you've purchased The Dyrt PRO directly, or following the conclusion of your free trial period, it is yours to use for a full year. If you wish to no longer subscribe to The Dyrt PRO in the future, please turn off your subscription auto renew.

If you purchased The Dyrt PRO through the The Dyrt website, you can turn off your subscription auto renew from your profile page on TheDyrt.com. If you purchased The Dyrt PRO through The Dyrt mobile app, please go to the "Me" tab in The Dyrt app user settings, which will link you to the correct app store to update your settings.

Those instructions can also be found here:

iPhone subscription instructions:

https://support.apple.com/en-us/HT202039

Android subscription instructions:

https://support.google.com/googleplay/answer/7018481

Refunds:

While The Dyrt can’t issue a refund for any payments made after your free trial of The Dyrt PRO ends,  you can reach out to the app stores for assistance, since they hold your credit card information:

Apple: https://support.apple.com/en-us/HT204084 

Google Play https://play.google.com/store/account

If you choose to cancel your PRO subscription, you can certainly still use The Dyrt for free to access information about tens of thousands of campgrounds across the US.