Introducing Cox Gigablast

After experiencing slow upload speed, i finally upgraded, to a $99 pla for the internet. They 're selling me a MODEm Arris CM100 doccis 3.1, then they asked me to upgrade to a new router, I bought a netgear nighthawk 1900, all in all I've spent almost $400 upgrade, hoping that it would increase my upload speeds or at least go back to where it was around 20mbps. I did get faster download speeds at 300++ mbps, Which I don't really need, I need faster uploads, UNFORTUNATELY, after spending almost $400 the UPLOAD SPEED are dismal  at 2-5 mbps. SHOULD I RETURN ALL THE GEAR THAT I JUST BOUGHT?  I don't know if my area 92630 supports Gigablast speed, but the guy at that COX SOLUTION STORE SHOULD have advised me, before buying that modem.