It sounds like they didn't know what the shelf live was but then
corrected it after you pointed it out. It sounds like what you really
want is an apology but those seem rare around here. I had a shop over
charge me $600 on a $200 bill because one A&P forgot to log out when he
went to lunch. The only reason I caught it was because I had left with
the plane at the time he was logged in. Even with all that evidence the
manager first told me the computer doesn't make mistakes. Then he later
sent me a fax telling me what happened and correcting the bill.
However, never an "I'm sorry" with my $600.

-Robert