Blackberry curve question regarding text messaging.?

SO I AM GETTING THE BLACKBERRY CURVE OR I ALREADY HAVE IT..LOL AND BESIDES MY PHONE SERVICEPLAN ALL IWANT IS TEXT MESSAGING AND I THOUGHT I WOULD TRY THE 200 MESSAGE ONE FOR $4.99 AND I DON'T HAVE ANY INTERNET SO IF I DON'T GO OVER THE 200 MESSAGES I AM JUST GOING TO GET BILLED $4.99? RIGHT? CINGULAR NICKLE AND DIMES YOU FOR STUPID THINGS SOMETIMES SO I JUST WANT TO MAKE SURE HOW THIS WORKS. ANY HELP WOULD BE NICE. =)