That is dependent on the person that set the g-line.
As was already stated, contact the network via their website and talk to them there.
For future reference, if someone does spam your channel, the proper procedure would be to:
1) Ban them from the channel
2) If they avoid the ban, then talk to the IRCops, as ban evasion is, normally, one of the few channel based operations that an IRCop will get involved with,
Please note that IRCops may (or will) require some kind of evidence regarding your complaint, so date & timestamped logs are a good idea to have available for them.
