Problem with Panasonic KX-HCM270 network camera

I have a couple of KX-HCM270 cameras around my property set up for
wireless connection.

I also set up fixed IP address of 192.168.1.90 and 192.168.1.95 on 2
of my cameras.

The problem is that my neighbor also has a wireless router and it
seems that at the edge of my property my cameras will loose my
wireless connection and try to connect to his.

I'm not sure how that happens since his router is set to 192.168.0.1
while mine is set to 192.168.1.1 and I thought since I gave them a
fixed IP they wouldn't try to connect to his network.

Everytime my cameras loose signal from my network if I unplug my
neighbors router they reconnect to mine.

How can I prevent them from "roaming" to his network?

Thanks

Joe