You ask your carrier to check it out. Even I would have to know your carrier and the towers plus the exact model phone to sort this out.
Let your carrier answer this one.
I was wondering of anyone can help me with a hige problem.
It is my second or third week trying to solve this with no luck.
I really want to buy Oneplus 3 but I live in Iceland and I'm not sure if the a3000 version will work, or if I have to get the a3003 one.
I am a total noob when it comes to MHz, LTE-bands etc. in phones.
I don't want to throw my money away for a phone that won't work.
Wich one should I get?

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic