Consider this a "hacking a non-computer system" challenge. It is a very useful skill even if you never send YC an application, since there are at least a few organizations which are isomorphic to AT&T customer service which are very difficult for you to opt out of using. (Your local department responsible for collecting taxes, for example.)
Tangentially - I ordered ISDN service from Qwest about a year ago. The business ordering agent (ISDN is only tariffed for businesses in Washington) transferred me to a supervisor, who then told me to hang up and call the retention department, and gave me the number. Retentions was able to transfer me to the person who was responsible for ISDN ordering, who was very knowledgeable.
Lesson of the story: Retentions agents can transfer you anywhere.
I think the mistake was admitting to having a mac. A rule of thumb is to pretend that the computer is Windows / IE so the rep can go by the book.
Where do you think the money comes from to offer the jump ship discounts? The sky?
But if you have other worthwhile choices that's great, until you run out of choices and have to go through the same system again. (Most ISPs seem to run a similar support scheme.)