What’s the cheapest way to call overseas?

Do you use local phone card, apps, operator service? I need to call overseas regularly, mainly to Surabaya and Medan in Indonesia. But I cannot rely fully on free apps because the data network in those 2 cities are not very good.

I use Skype. I have an online Skype number and for my folks when they dial it it registers as being local. I also use the call forwarding option or run Skype on the phone.

If you have data plan for your mobile, it's best to use global call, a smartphone app for cheap international call. Are you using iphone or android phone? this link is for apple store https://itunes.apple.com/kr/app/globalcall-free-$1.50-credit/id577717588?l=en&mt=8

There are a few really really cheap, practically free voip services out there that I've used in the past. They don't have the best call quality but you get what you pay for. I'll try to look some of those up for you.

Here's the company that I was using that was extremely cheap for calls to north america. The key feature is that they bill on a per second basis, so you get the full use of your prepaid credit. Like I mentioned, the call quality wasn't the best but it was adequate.

http://mywebcalls.com/

If you want to buy the credit and top up your balance on your international call app Global Call, you can get extra credit by clicking 'like' on the FB page until 11 July https://www.facebook.com/uglobalcall/app_193371724140087 it's worth the money, I just purchased 20 bucks credits and will get extra $2.60 (will receive this credit on 16th July)

appreciate the replies. i've downloaded the app from google play, just joined the facebook page so I can get updates on promo in the future. The connection was not bad and the rate is cheaper than skype for Indonesia.

don't forget to invite your contacts to download this app to, you'll get points and can convert it to real credit value. 10 points minimum to convert, equivalent to $10 free credit

Skype has been working great for me.
It has an occasional glitch every now and then.
It's free.