The major wireless carriers have never been shy about finding ways to jack up your monthly bill.

For years AT&T (NYSE:T)Verizon (NYSE:VZ)Sprint (NYSE:S), and the newly reformed T-Mobile (NASDAQ:TMUS) did not have to be very clever when it came to charging customers more because overages did it for them. The first three companies still make money on data overages, but the huge fees racked up by people using extra "minutes" to make calls has largely disappeared. The same is generally true for charges for excess text messaging. 

With the boon that was people inadvertently talking or texting too much having disappeared and customers being at least somewhat cognizant of data overage charges, the wireless companies have had to find new ways to pad people's bills.

Overpriced insurance 
One of the ways some of the wireless carriers pump up your bill is by tacking on a monthly insurance charge that allows a customer to receive a replacement phone should he or she break his or hers. On the surface that seems like a good idea, but in reality, the price paid may not be worth it.

AT&T, for example, sells its Mobile Insurance plan for $6.99 a month. The plan protects against loss, theft, accidental damage, and out-of-warranty malfunction. On the surface, it seems like a good deal, and if you've ever broken a phone, the peace of mind that comes from having protection is considerable. The problem is that it's incredibly easy to find third-party phone insurance that offers the same, if not better, coverage for less money a month with a lower device deductible.

SquareTrade, just one of a few providers of third party coverage, charges $5 a month, or $99 for a two-year commitment ($4.13 a month), and has a $75 deductible -- less than all of the major carriers.  

Consumer Reports, however, suggests you save even more money by not having smartphone insurance at all, writing in 2012:

Monthly premiums of $5 to $7 and deductibles of $25 for lesser-value phones to $199 for smart phones can add up. If you file a claim after 18 months, you'll have paid a total of $115 to $325, and the insurer might replace your phone with a refurbished model. Of course, accidents do happen. But in a 2009 survey we found that only one in five readers who bought a new phone in the previous two years did so because the old one was lost, stolen, or broken. Instead, keep your old phone after you upgrade so that you can reactivate it if necessary.

Instead of paying for insurance, most people would be better off setting aside the insurance premium each month in a fund that can used to offset a replacement or repair on the off chance you need one.

A broken phone can be a nightmare, but paying for insurance may not be worth it. Source: John Edwards. 

Unlimited talk plans that people are not using
Since 2009, the amount of data in text, email messages, streaming video, music, and other services on mobile devices surpassed the amount of voice data in cell phone calls, according to The New York Times. Younger people especially are less likely to talk on their mobile device and much more likely to use it to communicate via text, social media, and apps. That has not stopped people from paying for unlimited talk plans they don't take advantage of.

All four of the major wireless carriers include unlimited talk and text with all of their promoted contracted smartphone service plans (some have legacy plans sold on a per-minute basis). The only way around paying for minutes you don't use is using a pre-paid phone plan. Virgin Mobile, which is owned by Sprint, offers a 300-minute, unlimited text, 2.5 GB of data plan for $35 a month. That's cheaper than any of the contract offers from the big four; it's plenty of data for all but the heaviest users, and enough phone minutes for emergencies. 

If you don't use your phone for calling, pre-paid could allow you to opt out of paying for unlimited minutes you won't be using. 

Bigger data plans than needed because people are afraid of overages
The average U.S. consumer used 733 MB of data a month in the first quarter of 2013, according to Nielsen, The Wall Street Journal reported. That number may have increase in the past year-plus, but it's still likely many customers would be just fine with a smaller data plan than the one they currently pay for. T-Mobile does not charge overages -- it throttles down speeds after a user has exceeded his or her data allotment, but the other three major carriers do penalize users not on unlimited plans (which only Sprint offers to new customers).

The challenge here for customers is betting too small and ending up paying hefty overages, or betting too big and paying for unused data.

Aside from just switching to T-Mobile, the best way to make sure your plan matches your usage is to use the monitoring tools that all the providers offer. Sprint, for example, will send alerts if you choose to have it do so, when a customer nears the end of his or her allotment. These tools are not always easy to find, and it's reasonable to question why phones don't just have a real-time data meter, but it's possible to track use and adjust your plan accordingly if you really want to.

The ball is in your court
In most cases, wireless companies want to make sure you pay as much as possible while putting as little demand on their services as possible. A customer who buys insurance, pays for unlimited everything, and then uses very little is a dream customer. It's like you bought a seat at the buffet, but chose to have water and a half-plate of salad.

Avoiding cost pitfalls is not easy, but it's possible if you're diligent enough.