A little preparation goes a long way.
Prepare registration and verification before arrival, then check with a small ordinary purchase.
Before registration
Have access to your phone number, your own bank card and any identity information requested by the app. Use the official app-store version, keep verification codes private and follow the current in-app instructions as menus can change.
A practical setup order
Install the app, choose a suitable language, register your phone number and add a supported card through the bank-card section. Complete issuer verification. Check for unfinished steps before departure; successful linking does not mean every merchant or feature will work.
If a purchase fails
Capture the error: is it connectivity, a message, card verification or the merchant context? Check the connection and card status, then contact the app or issuer. If unresolved at the counter, use a backup and troubleshoot later.
After paying
Keep the transaction record and merchant name. For a refund, start with the merchant and original order, and check the destination and status of the refund rather than relying only on your card balance.