How do I make this phone work overseas?

I have enabled international roaming on my account - I did that before leaving California. However, the phone says no service. Would it be less expensive (and is it allowable?) to purchase a SIM card for Turkey? If I do that, do I have to set up an account with Turkcell and is that advisable for three weeks time? The folks at Turkcell don't speak much English and apparently most office things shut down (except for food and carpet sales) for thee week surrounding the end of Ramadan so it is difficult for me to get information here. I am told that it is very expensive to use the wireless aspect of the phone for internet so it may be worthwhile to buy the SIM card. (I will be traveling in areas where internet cafes are harder to fine.) What do you suggest?

is there a phone number specifically for internatial roaming. I tried an 800 number but it didn't work on a Turkish payphone. I can have my daughter call if I can give her the right number. Also does it cost anything to use the net here? It doesn't seem like of should

Thanks but the lınk just led me to a place to add a reduced prıce for ınternatıonal callıngç It dıdnit let me actıvate ınternatıonal roamıngç I called ATT on thıs and ıt was Sunday and they couldnit actıvate ıt for me on a Sunday because I hadnit had my phone for 90 days yet. I could call back durıng busıness hours durıng whıch tıme ıt ıs bedtıme hereç However they could charge me a monthly fee for the reduced rate whıch they have been doıng for two months. How I am ın rural Turkey wıthout access to ınternatıonal callıng at a shop or on my own phoneç I am serıously unhappy wıth ıPhoıne and ATT!