Slow speed & useless staff

I am paying for a 10mbps line and for the last 3 months the speed hasnt been more than 2mpbs I have tried troubleshooting with many different call centre agents with no help or no difference I was allocated a technician 3 weeks ago, was told i would get a call within 72hr I have called in 3 times after that to follow up and i kept getting told they will tell tech to contact me but still nothing up until now! ***