I had the two meg package which was automatically changed to the 4mb a while ago, I also have a WAG160N and had to do nothing to change it, however I never got 2mb and have never had 4mb, when I had the 2mb, I had average download of 1.25mbps and upload of 0.6mbps, since they changed it to 4mb it has been about 2.75mbps download and 1.25mbps upload. I think alot depends on where you live, how far from the local exchange, how many people are using that exchange. I find that in the evenings and weekends it goes really slow, and the best I remember ever having was about 3.2mbps. 4mb just means the your package and line is capable of 4mbps under ideal conditions (you live 2m from the exchange and no one else is using it) I don't think it actually means you will ever get it, using it wirelessly also slows the speed. have you tried speedtest.net to see what it actually is.
It may also take a few days or a week or two for QTEL to activate.