When we lived in the boonies north of Adelaide, we were initially in a dead zone for mobile phone reception. Not none at all, but very low quality and prone to drop out.
Our solution was to buy a mobile phone car kit and attempt to install it in the house. We had the base unit thingy and we had an antennnae to act as a mast for a mobile phone. But we never did get it working, it was very disappointing.
Eventually, of course, the mobile phone company improved reception to the area and it was no longer an issue (see! Ignore something for long enough and it will go away!) but now that we are moving into the new house, we have the same problem – worse if anything. There is *no* reception up the block. I guess we will be pulling out the old kit and seeing if we can install that mast somewhere and get the mobiles working!