In-app purchases are not refundable through Mozilla.
Where the user has purchase your app they may request a refund, refunds may be authorized by Mozilla, the payment processor, or the mobile network operator. These refunds will be authorized according to our refund policy in compliance with local consumer laws, the mobile operator's refund policy, and credit card refund policies.
If an app purchase is refunded, its receipt is invalidated. Therefore, you should always validate receipts to ensure proper licensing of any instance of an app. Apps that receive an abnormal volume of refund requests may be investigated by Mozilla.