Battlefield 4 server DDos Attacks

hello

i rent a server on G-portal.com, its runs very smooth and fast but since 2 weeks ago, is someone started with ddos attacks on our server so the server will be lagging horrible that makes it unplayable so the players are leaving and will join in hes server, he also stool things from our server like server name and the rules in our server, and evertime the owner is playing in hes server the lagg in our server starts again, and from the moment when our server is empty or he stops playing bf4 than the lagg stops and with some luck the most people are coming back to our server,

what can i do to stop this? the only option i see is switching to another provider