You will often find call centres are open earlier and/or later than advertised times.
Some call centres service the whole of Australia, so when advertised are open from 8am to 8pm are actually open 8am Sydney time until 10pm Sydney time (8pm Perth time). During daylight saving this gets changed again!!
A friend used to work on a call centre for a large Oz Bank. She worked till about 10pm or 11pm each night to cover WA etc.
I've heard the ad. too. I don't recall them saying that they're open later than 8pm, instead I recall them saying that they are open longer than their competitors...
You could always call and ask
