I can only assume that there is some problem with your network card, since that is about the only piece of hardware that should have a bearing on your connection speed that is different to the technicians test machine.

I'm assuming you have tried updating the drivers and checked the TX/RX speeds? It's a long shot as most if not all modern cards are equipped to handle networks far in excess of the speed of even the fastest cable connection.

I wouldn't like to say it could be a fraud as that is actually a very serious accusation. However, it is a well known and accepted fact that advertised speeds are optimum and realistically never achieved. Having said that, your performance is nowhere near what you have been quoted, so if the network card drivers bring no joy, get on to your ISP until they find out what the problem is.