You can request a tech visit.
Just be firm, tell them it is ongoing and the issue isn't being resolved and that you need a technician to come out and at least assess the situation.
They will normally be ok doing it on an ongoing issue like this.
Sadly it depends on who you get though...
We were living <400m (cable length) from the exchange and were getting <2Mbps and one agent told me that was an 'highly desirable speed'... but I will be honest, as with most things, if it is an intermittant fault, you might have issues - even if a tech comes out - getting it fixed, as the tech has to be there when it plays up to be able to see what is happening and try and fix it... and if you luck is like mine it will run perfectly for the time they are there... but the good techs will still check over everything and if possible might even try you on a different port or DSLAM to see if it is an port issue (which was causing my drop outs)