Don't feel bad about, to be frank when this wireless lark started, for several months I inadvertently connected to a local business instead of flatmate's wifi.
When the router owner moved out I was rather surprised that my internet service continued. When I realised what was happening I took the view that a signal penetrating my home without my consent was a bit like windfall apples from a neighbour's tree.
Nowadays every neighbouring wifi -- more than 30 of them at a casual count -- all are secured.