FreePBX installation and configuration, help needed

Hello everyone,
I’m quite new to VOIP and FREEPBX.
I would like to ask a few questions, I have installed FreePBX-5.211.65 with Asterisk 11 on Virtualbox. My host machine is windows7 and the host machine is set to linus ubuntu. In the installation i’ve set the network configuration to ipv4 only and manually put the ip on the FreePBX server. I can access it from my browser and setup anything like SIP trunks and extensions etc…
But the problem is when I try to call from my pc to a mobile number it keeps giving me the all circuits are busy now please call back later. I’ve looked everywhere starting from the forums here ending by all results for the pages by GOOGLE. I cannot ping my VOIP provider from my virtualbox, it seems it does not have internet access. Can anyone help ?
thank you for your time