My upstairs neighbors aren’t so friendly. Network hacked!

On Airplay and on my devices in the settings. I can see my neighbors jump on and off and actually renaming my Apple TV. Now, i wouldn’t be so concerned but, when i heard them talking above me clearly, i just noticed how thin the walls are here and I might have said my code out loud. If he could screen mirror me, then what else is there? He or she has the keys to the castle. So, actively I would see him change my Apple TV to Apple TV Main when I wasn’t using my machine. He has access to my network and I know how Apple loves WiFi but, in this case just resetting my passwords is all i need to do. I am sitting soon for a CompTIA+ and CISSP which is a cyber security specialist and have used some different tools. I want to catch him again jump on. He or she knows, the password to the network and the name will be changed but, there’s so many ways of targeting the strongest strength and who is connected. Is my next step only to change network ID and PW?