I am assuming that your laptop is connected via Wi-Fi to the Internet and is sharing or bridging the connection to its Ethernet interface, which is cabled to the Internet port on the SPA3102. If that's not correct, please explain the setup in detail.
What OS version is the laptop running? Are you using Internet Connection Sharing, or bridging? Have you tried the other?
Who is your VoIP provider? Have you tried another? IMO, Callcentric is best for avoiding NAT-related issues.
On the failing call to your mobile, can the VoIP user hear the mobile user? Can the mobile user hear the VoIP user?
When you call a landline number, is the audio ok in both directions?
What NAT and STUN settings are you using / have you tried?
If you can't get the Wi-Fi link working, you shouldn't need physical access to the SPA to troubleshoot a direct connection. Set Enable WAN Web Server to yes and you can then plug the device into your router and access it from the laptop. Put on your parka and go connect the SPA to a cordless phone base and your router in the basement. You can then change settings and make/receive calls from the comfort of your room.
Or, come on out here »www.wunderground.com/cgi-bin/fin ··· =bangkok