Boo,
Its normal to struggle a little with boundaries when we get close to someone. Perhaps many people wouldn’t be bothered even a little by him calling the bank. After all, he did cause the issue. It bothered you, and that’s totally OK too. We learn from our experiences with one another, and some boundaries aren’t understood until we cross them. Oops!
If the oops really sticks in his mind, such that he seems to be cycling and not hearing your assurance that everything is fine between you, then you can dive a little deeper and tell him how much you love him, including his mistakes, not despite them. How you respect his willingness to try, and how he will inevitably make mistakes. How those mistakes help you two know each other even better, find out more and more about one another, and grow your love and understanding of each other even more deeply, more well rooted. Said differently, you can help him see how these minor issues don’t put distance between you teo, rather, they meet up against your mutual love turn into greater closeness.
And congrats on not making it about you. Bravo!
With warmth,
Matt