@OCasasola 

Don't use MAC filtering it just not a good idea

Use the admin to restrict access to only certain devices, so the device you want to be able to adjust the router with and a phone if you want to use Teather app.

Randomise your IP so make 192.168.0.1 look like this 192.168.54.187 or similar ensuring the client list IP's aren't in the range you select, you can also also restrict the DCHP to only allow the number of clients you want, so if you have 10 devices make a client pool of 192.168.54.25 to 192.168.54.35, these are example numbers so make your own up and you can adjust the last two boxes but not the first two so XXX.XXX.???.??.

Ensure you max the passwords out as well and very random, the login one will take 32 characters and the wifi one which is where I suspect the neighbour is getting in from 64 characters, guest I'm not sure but it's at least 32 characters or turn it off if you don't need it, you can also turn the broadcast strength down as well if that doesn't inconvenience you.

Ensure both UPNP & WPS are turned off.

If you spot MAC's that don't match your devices in the DCHP pool use the blacklist function to block them, make sure you don't block your own though if you're using random MAC addresses on a phone or your PC.

Another easy way to spot things is always rename your devices, lets say the PC, it'll flag up as MS8423093Wintop or similar, rename it to something you can remember like "Random Box".