I cut costs way down by getting a "data-only" SIM for my iPhone and using a VOIP provider.

Call quality in poor signal (e.g. 2G) areas is terrible, but in urban areas with HSPA or LTE, it works great. I talk very little.

Look for the "flex-rate" plans that Rogers/Telus/etc offer. I sometimes pay as little as $5/mo if I don't use my phone, it scales with data usage.