the stripe API gets called even when a non "submit" button into the form is pressed

[xech3l0nx]

I have a form with various steps, the last one is the "review order" one with the confirm button, that charges the user.
this section is accessible only if the user has already a stripe single-use token generated for him in the previous step, where the form gets submitted and the response is handled.
By the way, even if the button in the final step isn't a submit button, the form gets submitted again, the stripe's api gets called with i don't know what values and the api respondes with a 400(Bad Request) status code.

EDIT(workaround)
changing the button to an a fixes the problem and the form doesn't get submitted again.

previous:

<button class="btn btn-primary" ng-click="charge()">Confirm</button>

edited:

<a class="btn btn-primary" ng-click="charge()">Confirm</a>