total newbie - did something dumb - please help

[Roberta Actor-Thomas]

I was in a hurry and didn't read enough of the guide before I started. I 
created sales which appeared in AR. However I didn't create the customer 
until a day later. Now when I enter the payment, it doubles the amount 
owed so it looks like sales in that amount were made twice. I have been 
trying to get rid of my first invoice and can't do that and it's 
appearing twice in the AR account.