I can't send texts for some odd reason?

I can receive texts, I just can't send them as of recent. I don't know why. I have an iPhone 5S. I reset the network settings and I removed/put the simcard back in the phone. I don't know what to do since everyone I know who has Sprint, isn't having trouble sending text messages.

Maybe you have to pay the bill. That's what happen to my phone one time. Because it was that time of the month