This makes no sense , if you move into an address that ( for example ) had broadband from another ISP , or you change provider and return the previous router ( or throw it away ) then the old provider WiFi ‘transmitted’ SSID’s don’t exist anymore, those network names are no longer broadcast ….if your device ( laptop , phone , tablet ) has remembered them ( even though they are no longer broadcast) you delete them from the individual devices ,( phone , laptop , tablet etc ) if the source of the network doesn’t exist anymore , how can it be broadcasting its WiFi ‘name’ ? .
The only way you would still ‘see’ these is if the previous router is still connected to the mains , switched on and broadcasting its WiFi network names , even though it doesn’t have an internet connection anymore.
Are you sure you are not just seeing neighbouring WiFi networks, as stated your question needs to be clarified, as it’s not clear what you are asking .
