I've a data card which has a limit of 2 GB up/download traffic per month. I've an office internet line which has an unlimited up/download.

I've successfully connected to VPN using my data card and by changing certain configurations like DNS etc., have also been able to use my office line for internet (verified by doing a IP check - returns the static IP of our office).

Now to my question - is it just a NAT which is happening or am I actually using my office line for all communication. Which one would reflect the usage/trace. The data card usage log at this moment does not reflect any usage (which is confusing since the VPN is over the data card connection).

Further more (theoretically), would the net be any faster if my office line is let us say 8Mbps and the data card is 512kbps by doing this as against directly connecting the internet using the data card.