Slow Speeds in Las Vegas

I'm currently having problems with the download speeds. We're paying for the 50 mbps download (premier) service tier, but we've not been able do get better then 20 mbps, with our average being 14 mbps. We often see speeds of 7 or 8 mbps. We've spoken with multiple technicians and are told that everything is green on their end. Then then try to 'send a signal' which never helps. Once, a technician came out to check everything and he said we looked good to go and the problem of not getting the right speed was something Cox had to fix. He also checked the 'nodes' and the house connections, but found nothing wrong. He did recommend we get a dual band router, so I went out and got that, and a new modem, too. This didn't help anything, our download speeds remain near 14 mbps. I feel like the technicians on chat support are almost confrontational. Every time I explain my problem (Them sending a signal kicks me offline, so I have to load the chat with a new technician) I'm told 'Everything is good on our end. You're getting a good signal and there's no packet loss. We'll send a signal for you to see if that helps'. Apparently my download speed doesn't matter at all since everything is 'green' on their end. I'm just stuck in this circle and sick of the run-around. Any help would be appreciated.