Is you house built of bricks and cement plastered?
Does it have tin roofing or tiles, even asbestos?
Does it have an electrical wiring and a lot of hanging wires outside?
If your answer is yes to all the above, then you have a problem because it all affects signal!
Even some types of paints affects signal.
The only way you can get around it is to encourage Econet to install a signal booster near your house.
If you are desperate and its critical to have signal inside your house, you can buy a signal repeater or a small femtocell, search them on ebay they are not that expensive