My sister-in-law dumped her phone line and is on a mobile broadband 12 month plan with Spark (60Gb at $65/month from memory). Out of interest I started looking around other providers and found that Skinny offer pretty much the same for around $20 cheaper.
It's been a couple of weeks since she started with the Spark plan - do they have a 30 day "cooling off" option to get out of it or is that's a U.S. thing only?

Cheers

Edit: Thinking a bit more, maybe this could be the case only if mobile reception is poor and is affecting the broadband.