unstable internet

I read the posts related to unstable internet, I've restarted my system, i've restarted the internet, I've unplugged the modem and the router, waited 5 minutes and plugged it back in. I've called customer service and waited over an hour. I've had a technician come over to my house and say theres something wrong with the system (but not within my house)...this issue has been going on since I bought your service, I've been paying full price for nearly a year, and the sercive is still terrible. We purchased the 2Gbps package, where barely getting 1Gbps, we can't stream anything in 4k, we get the ring of death for tv shows, youtubeTV and general youtube videos. Is this type of service acceptable to Xfinity?