I have charter service at my home. 30/4 package. Its fine through day, but the speed goes down round 5pm to 10pm everyday, 5mbps down, 4 mbps up. I contacted charter, and they say its due to my router. I have changed 3 routers and they have the same thing. The latest router I got now is netgear r6300, the previous are wndr3700 and wndr4500. Is it because their service or something wrong?