Travelers who own an iPhone usually learn too late that using it outside the US can be very expensive.

First the good news: The iPhone is GSM-based, the same as most places overseas. That means your phone will operate in most locations around the world just fine.

The bad news: It can be outrageously expensive. Some of you may have heard traveler horror stories about monsterous bills of $5,000 or even $8,000. Yes, it can and does happen unless you plan before you go.

One option for travelers is to temporarily use an international plan from AT&T. The plan for Canada, for example, is relatively inexpensive.  Europe, of course, costs more. The point here: If you plan to use your phone frequently – whether for calls or internet – check with AT&T about a short-term plan.

However, be very aware that if you use your phone a lot, you still might run up hundreds of dollars in charges. Ugly as that is, the plan might keep you from having a trip-ending phone bill in the thousands.

For some travelers, it may be wise to pick up an inexpensive mobile phone at your destination. Estimate your usage first to determine if this makes sense. Of course this will be for phone calls only, not data.

As for me, I have the iPhone to use it. These are the easy steps I do to minimize costs:

• Go into the phone’s Settings and turn on the Airplane Mode
• Turn off Notifications

• Turn off General/Network/Data Roaming

  Note that turning on Airplane Mode does not automatically turn off data roaming. This is the big ‘gotcha’ so remember this last step.

Is it really that simple?

Yes. I traveled all over Europe earlier this year and sure enough, my additional phone charges for an entire month were negligible.

Even with these adjusted settings, you can still use the phone-based applications as well as whatever you have stored in your phone’s iPod. Also, any GPS-based apps continue to work. For example, my auto navigation app worked perfectly in Canada even though the internet was disabled.

But I got the phone so I can connect to the internet for email, Twitter, Facebook, news, etc.

I hear you — the iPhone without internet is a real waste. A couple weeks ago in Mexico, AT&T detected my phone was outside the US. They sent me a text message that the international data rate of $19.97/Mb would apply. Trust me, this is a huge amount of money! By comparison, the European rate for their mobile phones is about $1.50/Mb.

The answer is to find a wi-fi spot.  I admit they are not as abundant as in the US but when you find one, it becomes your best friend at the moment.

Again using the Mexico example, my husband and I found a delightful second-story open air bar in Cancun overlooking the sandy shores and blue-green waters below us. Not only a beautiful location but also free wi-fi.  We turned off the Airplane Mode and had a perfect connection without the roaming charges.

I enjoyed margaritas, he enjoyed genuine Mexican Sol beer, and both of us tweeted away. Of course we also used the time to check our email and everything else on the net, all without additional cost.

It is very important to remember to switch back to Airplane Mode – and turn off Data Roaming if you switched it on – before you leave the wi-fi spot.  Forgetting this will certainly incur international roaming charges as the phone updates your email and other internet-based data even when you are not using it.

So how do you make phone calls?

I use Skype when traveling outside the US. Their long distance charges are very modest and easily worth the cost.

However, there also is a way to make free calls with Skype when you travel internationally.  All you need is:

• A wi-fi connection
• The other person is on Skype at the same time

In other words, if the person you are calling is connected to Skype via computer or mobile connection, you can talk for free. Obviously this doesn’t work if you are calling a landline phone.

If you use your iPhone when you travel, don’t forget there are many great travel apps available.  We previously compiled a list of more than 15 for you here. Best part, all of them are free.

Bottom line, take your iPhone when you travel but be very aware that roaming charges can be astonishing if you aren’t properly prepared.