If you live near a border, and the 'foreign' network mast is closer than your 'national' one, and has a stronger signal, you might be 'roaming' while at home.
That's why you don't tackle this at the electromagnetic wave level, you tackle it at the operator level. Or maybe at the phone level. Shouldn't the phone be able to recognize and prefer a local cell over a foreign one?
I mean, why does my phone prefer the crappy network that I have my crappy subscription with over the much stronger networks of the competitors? Why would this stop working when I'm near the border?
A phone can discriminate towards low signal strength cells of network A vs high strength cells of network B. Of course, the key word is 'can'; due to a lack of standardisation this will often fail to work properly for particular models.
Friend of mine lives 400m from a border. He has to call his cell provider monthly to contest the roaming charges he gets charged every month for using his phone at home. So far they've removed them every time.
