When ever someone says they made a ticket, ask for the ticket number. This not only confirms they ACTUALLY made the ticket but also allows you to follow up. The engineers almost never call the customer. They don't have "people skills".
As for your problem, sounds like a typical ingress issue on the upstream. Can you post your signal levels? Also how does the coax get from the street to the room the modem is in? Any splitters/amp/filters? If not, I would schedule another technician. Show them the T3 time out errors in the logs if you can. If they don't know what those are, they aren't competent techs and you should file a FCC complaint to escalate the issue.
BTW, Cox does track when a technician is assigned to a account that has had a technician out within 30 days. It counts badly against their metrics. More so for in-house technicians. Contractors usually could care less since they get paid per job and not as much on metrics and hourly rate. So rest assure you scheduling another tech will "punish" the last tech. Just make sure you have isolated all internet wiring issues to avoid a charge.(Assuming you don't have Cox complete care)