Add a simple OTP to woocommerce after payment

Dear all,

I am building a custom payment for one of our local banks for woocommerce.

I need once the user clicks on the place order button, I want to send the form information to the bank. Bank will send OTP to the user

I want to show an OTP form to collect the OTP that the bank sent to the user’s mobile.

I think I can draw an OTP from via

throw new Exception($html_form);

Then I can collect the OTB information the user will re-click on the place order button.
so I can resend the information to the back API.

but it turns out that

throw new Exception($html_form);

will strip out any HTML form.

How can I do this without changing the checkout page?