Unable to update or backup my iPhone due to pending in-app purchase

I made a mistake a while ago and tried to make an in app purchase, however the gift card I had didn’t have enough funds and I didn’t realize that it would go into my pending purchases. Fast forward to a while later, the app needs to be updated and I cannot get into it while the purchase is still pending. I can’t update it, downloading anything else, of even back up my phone while this purchase is still pending. How do I fix it?

[Re-Titled by Moderator]