You can use your PhoneGnome account directly on your iPhone to send SMS at rates that are generally much cheaper than the standard AT&T iPhone rates. This is particularly true for international SMS.

Here’s how:

1. Create a PhoneGnome account for your iPhone number. It’s free. Get a free account here.
2. Sign in to your account at http://my.phonegnome.com and activate the integrated voovox service - start with as little as $5. Go to the Features page and click Low Cost Internet Calling or click this shortcut on your My PhoneGnome home page:
   
3. Open Safari on your iPhone and visit m.phonegnome.com.
4. Sign in with your iPhone number and PIN. Bookmark this page, or save it to your iPhone Home Screen to get back here in one click in the future.
5. Click the Send SMS link

   

6. Enter the phone number (full inernational number) and type the message you wish to send.
7. When the recipient gets the message they will see it as a normal SMS from you to which they can reply normally. Their replies will arrive at your iPhone the normal way.