can I start texting right away or do I have to wait until the next bililng cycle?

You can use it right away, but it wont cover the texts for that month that you sent before you signed up. If you go on the AT&T website you can see how many messages you have used so you can check to make sure you arent going over your number of messages if you dont have unlimited. Be careful if you have the 200 a month. If you go over its 20 cents per message, not just the standard 10.

Right away.......go ahead use it.