After the 10th time, I got at least some info out of them:
"Hello JonG,
I understand that you would like us to extend the benefits of the promotion (Bonus ID - 3882) to your account.
I would have liked to process your request. However, the promotion (Bonus ID - 3882) started on April 19, 2010 and expired on July 19, 2010. While your account was opened in the first week of August, 2010. This is why we are unable to tag this promotion with your account and can't issue the additional 50,000 points.
We appreciate your understanding in this matter."
I am now trying offer 5748