Other mistake: Before the battle, the leader of the waterbenders says that he will have everyone extinguish as many sources of fire as possible. When the firebenders come up from the ground at the start of the battle, all of the torches lighting the city are lit.
Other mistake: When Aang creates the ice spear things during the battle, he throws them into the ground surrounding a few firebenders. The firebenders freeze as if frozen entirely in ice, despite being only caged in by ice spikes.
Answer: The TV show Americanized the pronunciations whereas the movie said them correctly.
The show is American, so with original characters you're allowed to say them how you want.