Newbie - setting up trunk - voipdiscount

Hello.I'm new in asterisk world. And i am having a little trouble setting up things. I have registered with voipdiscount and as i can see asterisk info, it is correctly registered (sip.sipdiscount.com:5060 .... 105 Registered )I am allso using softphone - X lite and it is correctly registered as extension 500. Now i would like to make calls from x lite, and somehow i can't make any. How exactly must i configure SIP trunk and outband rules if i want to make calls to Slovenia? Prefix to call to Slovenija is +386 and, we have prefixes for regions, for example 4. So if i want to call our number from some other country i have to dial +3864XXXXXXX I was trying now with warious settings but i could't make any calls. So i would like to set up asterisk this way: If i dial for example 42317777 the call would go over voipdiscount. Or do i have to dial +38642317777? In X lite?Or is better solution to have some prefix to dial through this trunk? After that, i would like to make another trunk: With GSM gateway - so i could make calls to our GSM prefixes over it. We have several different prefixes for our GSM network (041, 040, ...) So if i would dial 041999999 the call would go throug GSM trunk. Or, again, is better solution to have some prefix to dial through this trunk? Best regards Klemen