international calls

I have an iPhone 8 which I love, however, it won’t call the Netherlands. If dials the number and then after a short wait it drops the call. The strange thing is that it does ring a couple of times in the Netherlands. Because I think the calls has dropped my partner keeps thinking I am hanging up on her.

Have reset the phone several times, spent endless amounts of time talking to my service provider but just cannot seem to resolve this............HELP PLEASE