Problems with the neighbour

I am an easy person. At least I'd like to think so. Flexible, open and social. Yes sounds good. And some friends of mine, try to refrain from commenting now ;). Now I'm having trouble with a neighbour, but it's not what you think. When I moved in I had a chat with one of the neighbours about network. He's getting his for free from his company, and he didn't mind that I would hang on using his. Problem was it didn't work enough to stream tv and have enough connection at all times. Cement walls. So I caved in and got my own network. 50 friggin francs a month, but since I use my computer a LOT I had to. Since about a month my computer keeps on connecting to his network, and I cannot connect back to mine. Keeps on giving me the message "cannot connect to network", then "diagnose problem", which it never does. Think it might have to do with me moving my computer from my dining table to the bar. After the shoulder op it was easier for me to use the computer standing up, rather than sitting comfortably at the table. But if I pay 50 francs a month for a box with 6 ports, I should be able to use it everywhere in my apartment. Not?