Please Help...

I know this is probably covered some where around here, but I have a very slow and limited internet connection where I am over seas; so very hard to search.

I have taken my cingular treo 600 to this country. I am using a local sim card and it has worked perfectly in the main city. I got on the plane and went to another city in this country, and now the phone is not working. My friend with a samsung phone has no problem. My sim card works in his phone in this new location, but neither my sim card, nor his sim card work in my treo.

after removing the sim card couple of times, I am now able to get the name of the network on my phone and get some antena bars. But when I make a phone call, I get two different tones and the phone hangs up.

Is this a way to manually adjust the network setting on my treo? I checked NETWORK under Preferences, and all I see is just Cingular and Cingular Express. No way of manually changing the mhz settings.

suggestions?

p.s. i will post this under other forums and websites to see if I can get a solution