Birthday

Okay so I was setting up my Apple Pay and when asked for my birthday keep in mind I’m here doing his after a long day of work and I entered the wrong birthday my birthday is June 12th and for some reason I put in June then Thought it said birth month instead of day and asked for the day and not the actual month and I put 6 so I put 6/6 when it should be 6/12 lol I don’t know how I managed that one but now it will not allow me to go back and change it how can I do this??