I ordered Cox Premier Internet, but I'm not getting anywhere near 50 Mbps

On speedtest, the most I hit is around 35 or so. I saw another similar post on the forums, but I think I need help from a technician to get 50 Mbps, something to do with:

"Cox technical support rep enabled DOCSIS 3.0 for account and I'm now seeing download 55.30 Mbps, 20.6 Mbps upload on wired laptop.  Great tech support.  Thank you!" by Wanderer88

My modem is a Motorola SB6141. Any help would be greatly appreciated!