Calls to landline abroad(Greece) doesn’t work, mobiles abroad closes down.

Hello guys and girls! 
I have the mobile package with unlimited calls and SMS in EU, and unlimited Data. 
Everything works fine calling in the Netherlands. When I try to call Greece, there is the problem. 
1) When I call landlines in Greece, it rings and when they pick up, they cannot hear me and I cannot hear them. It’s just empty…
2) When I call a Greek mobile phone, we can talk normally but at 15 minutes and 32 seconds, the call ends by itself. Every time. 
And I have to call again…

That doesn’t happen with any calls I make to Dutch numbers. 
Is there any security settings when calling foreign nymbers?