There are plenty of cheap ways to make calls when abroad, including a combination of local SIM cards and Skype. But setting up these methods can be complicated and time consuming, and it’s often more convenient just to use your cellphone. It’s no wonder, then, that many people get hit with high roaming charges when they travel out of the country.

But on a recent trip to Mexico, I hit on one way to reduce the international bill, at least for travel to some countries: Call your mobile service provider ahead of time and temporarily change your phone plan. I had heard of corporations doing this before their BlackBerry-toting employees go abroad. So I took the 10 minutes to try out the method myself.

A week or so before my trip, I called Verizon Wireless and changed my plan to a nationwide plus Mexico plan for the time I was gone. With such a plan, assuming I stayed within my allotted minutes, I could call the United States from Mexico, and vice versa, with no roaming charges of 99 cents per minute. In addition, I changed my data plan to a global one so I could check e-mail and the Internet on my BlackBerry. Then, when I returned home, I immediately called Verizon and changed my plan back.

According to Verizon Wireless, the whole change cost me about $30 extra, a lot cheaper than if I had been charged 99 cents a minute for the 200 minutes of calls to the States I made while abroad.

A Verizon Wireless spokesman said customers should call customer service representatives before going on their trip as I did “to ensure they are signed up for the right plan during the time they are traveling.” And it’s not just Verizon Wireless that will allow such temporary changes. A spokeswoman for AT&T Wireless had a similar recommendation. “First and foremost, we recommend our customers reach out to us before they go on their trip so we can ensure their phone and plans are set up properly to avoid any surprises on their bill,” she said.

When you call to change your plan before you go and then reverse the change when you get back, the wireless providers will  charge you only for a portion of the new plan’s monthly charge (assuming your trip was less than month) or just for the calls you made while abroad, depending on the plan. For instance, customers “will only be billed for the time period” of the trip, the AT&T Wireless spokeswoman said.

Still, this means that certain plan features — like the number of minutes available for you to use to make calls or check the Internet — will also be prorated for that time period. So let’s say you have 1,400 minutes of monthly calls, if you’re only on an international plan for two weeks, you’ll only have 700 minutes of roaming charge-free calls when abroad. That’s why it’s important to make sure the temporary change has a start date — even a backdated one — that gives you enough minutes, said a Verizon Wireless customer service supervisor.

There are also a few other caveats to this method. First, depending on what country you’re going to and how much you use your phone, temporarily changing your plan may not result in big savings.

Verizon’s bundled international plans, for instance, are only available for two countries. In addition to the Nationwide plus Mexico plan, Verizon Wireless also offers a similar plan for Canada. (The plans don’t offer unlimited calling between Verizon mobile phones and free text messaging.) AT&T Wireless, meanwhile, also offers similar plans to the same countries, and Sprint offers a $2.99 per month discounted Canada roaming rate of 20 cents per minute, down from 59 cents per minute without the add-on.

For travel to other countries, however, the wireless providers generally just offer plans guaranteeing discounted roaming rates. Verizon Wireless, for instance, offers a $4.99 per month “Global Value Plan” that reduces customers’ per-minute roaming rates for about 130 countries, AT&T Wireless’ World Traveler service offers similar discounted rates for $5.99 a month and Sprint also offers a $4.99 per month similar service.

The discounted rates offered under such general international plans are often still expensive, especially if you plan to use a lot of minutes when abroad. If that’s the case, you may want to consider instead setting up your phone to work with mobile Internet calling services, as recommended in a New York Times article in January.

In addition, because of different technology, not all phones will even work abroad. Any Verizon Wireless phone, for instance, will work in about 40 countries but only ones with global capabilities will work in more than 200 countries. (Verizon Wireless will provide loaner devices for those traveling to countries where its regular phones don’t work.)

Resources from wireless providers can help you figure out your best option. To see if your AT&T Wireless phone will work where you’re going and what the rate and service availability will be, check out this Travel Guide from the wireless provider. You can also see more about where AT&T Wireless coverage is provided and available rates here. Meanwhile, more information about Sprint’s international voice and data options is available here, and more information about Verizon’s options is available here.

A spokesman for T-Mobile, meanwhile, said that to use T-Mobile phones abroad, customers can temporarily add T-Mobile’s free international roaming feature (international voice and data roaming rates can be foundhere) or pay a $5 fee for discounted roaming rates. T-Mobile will also let customers unlock their phones to use a local prepaid SIM card, if they call customer service, the spokesman said.

Have you tried temporarily changing your cellphone plan before going abroad? How did it go? What other tips do you have for cost effectively using a cellphone when abroad?