If the travel charger clearly states it can convert to correct voltage I don't see how that would be a problem. While Cingular would have no clue (because they aren't the manufacturer), LG should be able to answer your questions. My guess is that LG won't guarantee that it will work correctly and if your battery is damaged they won't be liable.
I can't seem to get a straight answer to my question from Cingular or LG. I have a relatively new LG cell phone, model CU500. It came with a "travel adapter" that I use here in the U.S. to charge the battery. The adapter reads "Input: 100-240V..." With the use of a plug adapter to fit into the wall outlet, can I use this LG Travel Adapter to charge my phone in a foreign country (Turkey) that has 220V instead of our 110V?