The US Federal Communications Commission (FCC) has started an informal investigation into Apple's refusal to allow Google Voice to be used on its iPhone.
And it's not only Apple that's in a spot of bother. The FCC is also asking questions of AT&T, partner to the iPhone in the US.
The FCC sent letters to the companies asking them why they rejected the Google Voince application. Earlier last week Apple said it wouldn't distribute Google software - the reason appears to be that it doesn't want any competition on the apps front.
AT&T doesn't want people to start using applications like Google Voice. It wants its customers to pick up the telephone and pay AT&T for the privilege.
The FCC said in a statement that it considered its duty to promote competition in the wireless marketplace.