router/modem highjacked

The one screenshot only shows 4 devices in your internal network, one of which is the router and you seem to have at least one computer and one phone so that's two more devices.

You really need to post clear and complete shots to explain what you are seeing, that means NOT using a BlackBerry to post the screenshots but an actual computer.

Also list all the devices in your network, do you have an additional router, switch, wireless access point? How many computers do you have? Are they using wired or wireless connections? Do you have a smart TV or BluRay player or a game console like a Xbox or Playstation, do you have additional phones or tablets?

Is is the wireless password you are changing or the router's admin password?

Download Netscan and have it scan your network, post a screenshot of the results:https://www.softperfect.com/products/networkscanner/
In Netscan enable the option to "Resolve MAC addresses" on the "Additional" tab under "Options": https://www.softperfect.com/products...canner/manual/

I'll also move you to the Networking section.