Who I have the same questioned this topic

For the 1st few months my Ethernet connected desk top had a good download speeds using a cantenna on a 4G LTE 10 GB dataplan.  I have no other devices connected and WiFi is disabled on the router.  For the past 6 weeks  speeds are usually less than 0.6  from 11AM to 9 PM.  Weekly, I have opened  tickets, but they get closed when the techs determine there is "nothing wrong".    I expected and am still paying for the advertised 5 - 10  speed - but getting dial up speeds that seriously degrade the usage...      Seems like cell tower congestion to me, but no one at Verizon I have talked to will admit that is the problem.....  they keep opening tickets and closing them without any resolution.    I cannot recommend Verizon to anyone else.