If you accidentally upload the wrong receipt to a transaction, don’t worry, you can easily change this.

From the mobile app, tap on the transaction, then tap the "View Receipt" button. From there, tap the 3 dots on the bottom right hand corner then you can either replace the receipt by taking a new photo, or uploading a new receipt. You can also delete the uploaded receipt.

From the web page, click on the transaction to expand it, then click "Delete Receipt". You can then attach a new receipt.