After making a purchase in Fishing Clash, you should be receiving a receipt from the Google Play Store. There, you will find all the information about the purchased item: date, hour and a GPA number.
The GPA number is your transaction ID and has the following format:
By providing this number we can verify your purchase.
If you don't have the receipt for your purchase, you can always review all your purchases made on Google Play by signing to https://payments.google.com/ (please use your Google account login and password)