Change Name Displayed in modem/router

Hi,
im new mac user... learning... blablabla

so; i got a second hand mbp late 2008.
i bought snow leopard and upgraded.
erased the hard disk with the disk utility.

but my problem is that in the settings of my modem/router my macbook has the name created by the previous owner, including his first name.

i tried changing names in both network>advanced as in sharing, but both didn't work.

maybe it matters that i connected before restoring, and therefore my modem remembered it?

details: MBP late 2008, snow leopard, wireless connection, Thomson TG787v

 

Thanks, i figured it should indeed be found there.
i have tried to change the device's name in the "configuration" but it was set back.
ill continue to try, maybe look for a button to wipe, or maybe i missed the button to save all new changes.