VoXaLot over 3G?
 

I'm not sure exactly how to configure this. I have a Nokia e61i and my VSP is Callcentric. I have 3G over AT&T. I can register with VoXaLot over 3G, but whenever I try to make a call, it simply tells me that there is no WLAN available. Perhaps I can configure a dial plan? I don't really know where to start, so if someone could help, it would be much-appreciated.

I won't be of much help, since I don't know what you need to do step by step to configure it, however, one suggestion is to try setting up CallCentric directly on its own on the phone and see if you can place calls that way....if that works at least you'll know all that needs to be done is Dial Plan configuration for VoXalot to work as well

Also see if these Nokia related setups help in any way Nokia Configuration Settings - Voxalot FAQ

Again, no familiarity with the Nokia setup, but from the message you describe this sounds relevant from the guide:
"The IAP (Internet Access Point) may need adjustment for the Voxalot entry when required -- the Truphone application takes care of roaming b/w IAPs for Truphone only"

I don't know if this is of any relevance, but in a simpler Nokia phone with no wi-fi - the 6070 - I had quite a bit of trouble getting set up to use a simple Java application that sends via grps data ...

The problem was defining the connection when I used a different SIM card in the unlocked phone. To change networks there are about four different places in the menu, on different branches of it, including configuration settings, default configuration settings, activate default in all applications, etc

After a total lack of help from Nokia, in which their CS accused me of fraud for the phone being unlocked, or they suggested that they didn't support third party applications by people who couldn't program properly and who should read the Java application notes on the Nokia website (and I was hung up on when I said that I'd read that the software worked on a Sony Ericsson and other Nokias), I eventually found yet another part of the menu that Nokia's tech support hadn't even mentioned - preferred access point, still set to Orange when I'd put in a Virgin SIM and switched all the other settings to Virgin.

So apologies if it's an off-topic ramble and turns out no help, but take another tour through all the phone menus for default and preferred options on connectivity, access, configuration and so on ...

You need to install the new Nokia SIP settings application. In there somewhere you can Allow WCDMA calls. Can't remember exactly. A right pain to configure. You don't set an access point. Just turn the phone on and off again and it will auto register using 3G. Doesn't matter anyway as you can't really make any decent calls because you can't choose the G723 codec so bandwidth is too high.
Instead just download Fring which uses a lower bandwidth codec and will work albeit hit and miss.
I have tried just about every other possible solution to get my incoming Sipgate number and outgoing free calls to work over 3G with very little success. Let me know if you have any more luck. Otherwsie I am just waiting for the fatser HSDPA speed here.