8 Upstream Channels Are Not Bonding

I recently upgraded to the Arris SBG8300, which is capable of 32 downstream channels and 8 upstream channels. All 32 downstream channels are bonding, however, only 4 upstream channels are showing up in the gateway control panel. Would someone please be able to tell me if Cox has a limitation of 4 upstream channels or can this be changed by request? I have gone around and around with technical support and they don't have a clue. I was asking them to transfer my ticket to the Engineering department but they scheduled an appointment for a technician to come out and investigate. I have my doubts that a technician is going to be able to help. TIA!