Unable to use online banking app on new phone

I have a new iphone and have tried to upload online banking app onto my phone. I download the app and then I am asked for a credit card number and pin number. I have tried entering credit card and savings account and none of these are accepted. I am losing the will to live. It's counter-intuitive as all you should need to access would be a username and password. I have emailed them but no response. I refuse to sit on the phone for hours. There must be a work-around. Online banking should make things easier not more difficult.