I don't feel like the op in my minecraft server?

I've set up a minecraft bukkit server, it runs well, It has a few plugins like, setspawn, world edit, etc. I haven't done that much apart from make a design world which is a castle. I download the mob arena plugin and made an arena, with the signs, knight, archer, oddjob, etc.
I click knight and then tried testing it out but the monsters weren't spawning so I deleted the mod, now I'm stuck as a knight, and every time I join the server, I get the knight tools, I have hearts, and food, I never used to have that because I was op and I could fly around because when I first made the world, it's creative for me.

**Tried:**
-I've tried /kill to kill myself and I still spawn with them
-Completely delete all of the Mob arena files from plugins
-Restarted server
-I've deleted the signs

Go to where you installed the server they're will be a.txt file called ops go there and write your minecraft username that might work
if not then don't use bullit use the original server creator made my mojang AB