Xbox live MTU problem please help!?

im so frustrated with xbox live right now!! i finally thought i fixed my live after being on the phone with my internet/cable people and then it signs me off again! now its saying my MTU should be set higher? i've googled and youtubed trying to figure out how to fix it but everyone keeps saying to go to the WAN set up menu when i go into my account i don't have that option..all i have are: basic settings,wireless settings,wireless guest settings,wps settings,wifi multimedia,gateway status,connection,set password,backup,event log,diagnostic,dynamic dns,port blocking,port forwarding,port triggering,dmz host,lan ip,remote management,and Upnp. i list them all just in case one of you guys can tell me which one i should be going to since i don't have the WAN setup. its a CGD24G model netgear. and its not connect directly to the modem im using wifi connect. modem is in the other room. some one please help a girl game again. thanks and hope someone can help me out!