IAP not success with delayed test cards

Hello,
I have a problem. IAP works fine, but when I try with slow cards, I need to recheck whether the transaction is approved or not. How can I do this? (It is approved after 2 minutes on average, but I have to question whether the transaction is approved or rejected)
Thank you

I created a restore button. If billing has been successed this metod set to restored.
This fixed my problem.


Thank you.