You can't upgrade it from HD3000 to HD4000 without replacing the processor, as it is on the same bit of silicon. They must have shipped you the wrong laptop or you ordered something else. Find the invoice and check. If it does say HD4000, demand to have it replaced, as there is a MASSIVE difference between them.
EDIT: so yes, she is trying to pull the wool over your eyes. They probably want to get rid of a bunch of old chips.