Well, now you can! If you have aniPhone or iPod Touch, the SipPhone on iPhone  ($6.99) from VNetCorp allows you to make and receive office calls from any wireless hotspot, anywhere in the world, without using your regular cellular phone service. Your iPhone becomes an extra office phone that rings when your desk phone does, for free! Think of it as a cordless phone that works while you are in the office and also from any wireless hotspot.

To set up your iPhone as a wireless SIP phone this is what you need to do:

1. First, in whatever PBX or Voip service you use, create a new endpoint and write down the SIP ID (or just get a SIP ID)

2. You will also need the IP Address of your PBX or Sip Server 

3. You will also need your account name and password (if your system requires one)

4. Then simply download the SipPhone iPhone application through the App Store (search for “SipPhone on iPhone”) and configure it.

1. Open SipPhone, Tap Accounts, then Tap Edit.

2. Tap ‘+’ and you should see the following:

3. Tap Domain and enter the LAN IP address that you wrote down earlier.

4. Tap Username and enter the SIP user/account name that you wrote down earlier (for example, 10007.)

5. Tap Password and enter anything as a password; some systems do not require a password, but SipPhone requires you to enter one.

6. Tap Save, Tap Done, then Tap the on/off toggle button to turn SipPhone on.

3. Now all you have to do is connect your iPhone to your WiFi network. 

That’s it! You can now make and receive VoIP calls with your iPhone or iPod Touch using a wireless connection and not using up Cell minutes.

NOTE: To use SipPhone on an iPod Touch, you will also need a microphone or a headset with a microphone.