cant connect to verizon router

hi, ive been having this problem for quite some time now. whenever im at my grandparents house, my macbook pro doesnt seem to connect to their wireless internet. i have no clue why, it connects but then i dont get internet access?
what do i do? this is getting quiet annoying

Turn off airport from the menubar, then open network prefs > advanced > delete their network from the list. Click Ok, then Apply. Now open keychain access (in Utilities), search for their network, and delete ALL instances of it. Now turn airport back on. Rejoin the network with the password as if for the first time.

ok, so now im getting connection but it wont go on the internets, what do?

its really slow and can't reach the servers

Sounds like a problem with their router.

is there a wayn to fix that?