Audio won't resume after phone call on iphone 4 ios6

hi!!! really need help.. don't know what to do... I build my application, for ios and android, an on android everything it's ok, on ios, on iphone 3gs ios 5.1 everything it's fine too, but on iphone 4 ios6 don't understando why when I'm on my application, and I received a phone call, when the call finish I came back and have no audio at all!!, this only happend on phone calls, I can minimize open other applications, my application have facebook connect, gamecenter, links to other pages, and everythings works fine, I can back to it without a problem at all, it's only phone calls, and only on ios 6, all versions tested are exact the same. so really I don't know what I can do about it... please reaally needdd help!!

thanks! and sorry my bad english

forgot to tell, I'm using unity 4

thanks!!