Stuck in Creative mode for Multiplayer

I installed Minecraft yesterday. When I was playing single player in survival mode. (I have not yet tried createive mode.) I haven't installed any mods and I haven't changed a single setting (I haven't even opened the console).

Today, I connected to my friend's server. I thought he had it set to Creative mode, but he had not. For some reason I spawned in Creative mode. How do I get out of it? Him and the other players were in Survival mode, which is what I want.

Any ideas?

As you don't have OP priviliges yourself, you will need to get someone who does to change it for you. The easiest way to change it is for them to type the following command in-game:

/gamemode 0 <CharacterName>

Where <CharacterName> is the case-insensitive name of your character (without the <>). That will update your game mode to Survival.

You can read more about the gamemode command on the Minecraft Wiki