Look at MobileVOIP. Free wifi and 3G app (will use whichever is readily available). Comments look good on it, etc. etc.
And if you're unhappy with features on the iPhone, leave a comment for Apple on their Contact Us page, don't come into an Apple support forum and instantly finish your very first comment with 'i'm just venting because I come from an android background and im anything but impressed'. It just sounds like you're complaining because you didn't do any research into this matter before getting a new phone.
Anywhom, long story short. Look at MobileVOIP, or y'know, browse the App Store, it's there with a search function so you can use it.