Can you tell us from which country you are and from which countries you used the VPN? And what did they say exactly about your breaching the Terms?
They indicated on their terms, that Montenegro is not prohibited, so they can not give this as reason.
I am a citizen of Montenegro, i used the betcoin.ag site from Montenegro, on a mobile phone (mostly, not sure if i ever logged in from pc) WITHOUT any VPN.
Well, you can read their email reply (they sent me ONLY one email saying my account is closed, i sent emails later asking about my money but they just ignore me) above, they accuse me of "playing from a banned region"