i know you are improving to be professional maybe it was a bit rude but you have to understand that customer are living at 10.000 km from thailand and they invest a big part of their money with us cause they trust us.
So when they see a mistake like this they ask themselves how you will do for the rest...
Just tell you this cause this is not the first time that this kind of mistake is done , so yes please accounting have to check carefuly before to send a receipt.