I did some locum work for a big company. They advertised the shift as as 9-6 and sent an email to confirm. The store closed at 5 so I had to leave at 5. This was an error on their part as it always closes then (I did not know opening times). They sent me an email today (4 days later) with an updated confirmation of the shift as 9-5. AIBU to request payment for the additional hour as that is what they advertised and I agreed to?