Text messages not being delivered on Iphone 4?

They were working just fine and tonight it's just not working. It always gets stuck towards the end and I get the 'not delivered message' I tried resetting my network settings, but it didn't help. How can I fix this?

There can be a couple reasons to this, one is if you're using a Wi-Fi connection that may be not your own connection so check to see if you're on the correct connection. Another reason could be that if you are in fact using Wi-Fi, that your Internet bill isn't paid for thus not allowing you to deliver any messages through Wi-Fi. In some cases this happens, the person that you are trying to send to might not have good or pour connection/service resulting in blockage from anything being received. Hope I helped.