I Have a Dedicated CSS Server Going But....

I can't change any of the commands.. My uncle created me a dedciated internet server for CSS and I've been given admin for the server. I can't seem to change anything though.. Everytime I try a command like changelevel, sv_alltalk or sv_gravity It either gives me an error or it doesn't say anything and it doesn't change the server. So is there different commands for an online dedicated server?

Thanks

mp_startmoney x

where x is the value of how much money you want to start with (between 800-16000).