To know what plan you should be on (and if you're currently overpaying for what you need), you first need to have a good idea of how much data you use each month.To do this, log into your wireless account online, or visit your carrier's mobile app on your phone. There should be a section for Billing and Usage, then navigate to the Usage section. Write down your data, text, and phone usage for the past three to six months to get an idea of your average usage. Did you go over at any point? A tiny bit, or a lot? Or are you regularly way under your limit?Looking at my own stats, I found that I regularly use around 1.3 GB of data each month, but I did exceed my data limit on several occasions last year during the months I was traveling a lot.Next, head to the "View or Change Rate Plan" section (which may also offer a snapshot of your average data use) to see how your data use compares with your current plan, versus others.For me, it's pretty clear that my current 2 GB limit is reasonable for my usage habits — the next level down, a measly 300 MB a month, would not cut it. If you regularly exceed your monthly allotment, it might make sense to spring for one to two more GB a month; if you're paying for 3 GB and using less than 1 GB month each month, it could also make sense to drop down to a lower tier.If you're open to switching carriers, check out Wirefly or a similar site to compare rates for different wireless vendors. Here is a quick guide as to what phones work on what wireless networks. In my case, both AT&T and T-Mobile have plans that work for me, and are cheaper than what I'm paying for now. Score!If you're locked into a two-year data plan, some carriers will pay your cancellation fee (or a portion of it).