You can always make refunds through basecamp and the yetipay mobile app, but you can also make refunds on the card machine itself using the new yetipay payments app.
To make a refund:
In the yetipay payments app, tap the menu button (top right of the screen)
Choose All transactions
Enter the default refunds pin (1254)
Find the transaction you want to refund, and tap on it to select it
Tap the Refund button
Refund the full amount of the transaction, or, for a partial refund, edit the amount before pressing the Refund button
(optional) add an email address before pressing Refund to send a refund confirmation email to the customer
How the refund modal in the app looks: