Note: this will only allow you to make calls to US numbers, excluding Alaska and Hawaii, as that's all the Whistle Phone service supports. See the last paragraph of this post for alternative options.
- Go to whistlephone.com, download their software to your desktop, and register for a free account.
- Download the CSipSimple app from the android market
Here's the QR code:
- Open CSipSimple, choose the integration you want, then click Add Account. Then scroll down to Generic wizards --> Advanced.
- Account name: whatever you want
- Caller ID: your whistle phone number
- Server: proxy.whistlephone.com
- Username: your whistle phone number
- Password: your whistle phone account password
- Use TCP: leave unchecked
- Proxy: proxy.whistlephone.com
For outgoing calls, it seems to take a good while to connect (about 15 seconds), then you have to listen to 10-second ad. Incoming calls seem to go through pretty quickly, though, and neither you nor the calling party has to listen to any ads.
The CSipSimple app mentions lots of other SIP providers, so maybe one of them is free and has better connection times for outgoing calls (perhaps even ad-free), or will even allow you to call different countries for free, but I haven't checked any of the others out yet.
Update: since I posted this, Whistle Phone limited inbound and outbound calls to 20 minutes. you can read more about that here: https://www.whistlephone.com/naywa. also, I did take the time to look into the other US SIP providers mentioned in the CSipSimple app, and none of them allows you to make free calls except to users using their service. but if you do hear of a better SIP provider, let me know!