Poor Internet Quality

Cox: I've repeatedly had Cox come out to test my internet and supposedly everything is good. I continue to have streaming video issues which point to Cox; even after re-booting everything. Netflix: low quality picture. Like I've been downgraded to a lower stream rate Hulu: low quality picture. Amazon Prime: Every couple of minutes, the video pauses and/or the sound cuts out for @ 1 second. I have the 50Mb/s service and speed tests confirm at least 25Mb/s so not sure what the issue is. Everyone keeps pointing the finger at the other person which is frustrating. This has been going on for years but is getting more annoying as we watch more streaming shows. Cox, please help...