I believe you can't do that - not without jumping through a lot of hoops anyway. It's one of the "key" fields that uniquely identify a customer. (After all, there must be many M&B members with exactly the same names). I know this because I once tried to set up an account for a relative who had forgotten they already had one. It wouldn't let me use their name/DOB combination. To change a DOB (for example, if you'd entered it incorrectly) I think you'd need to send copies of ID showing the correct date. That's what they make you do when you need to change a mis-spelled name, for example (I've done that too).