I'm with jamieb, I've experienced this with Sentech and with iBurst, wireless companies generally don't give a flying fluck about your problems. "You're the only one with the problem" jumps to mind, heck, TheRodent even went as far as to :
a) Write Linux drivers for Sentech's MySuck modem
b) Determine that their proxy servers are wide open for (ab)use from ADSL users and in turn we get blamed.
So the same thing goes for iBurst, we had to find out ourselves that they change the MTU settings whenever they feel horny but couldn't get laid, they switch from using their stupid proxy without notifying customers, WE had to determine their capping was flawed (and might I say, suffer the consequences)
With all this effort a service is still shyte and customer service even crappier, so why in the world would I want to stay with iBurst?
jamieb, cancel now, it won't get any better, there is no light at the end of the tunnel (it's probably an oncoming train)
Rather waste your money on ADSL (which should be going 1mb soon anyway)