Did a little digging after I realized I'm also not getting any replies to the SMS I send to people. Apparently, when my phone was activated, my data and messaging plans were deactivated from my S2, but only the data plan made it over to the S5. So I currently have no messaging plan.
What's frustrating about that, I had the "Messaging 200" plan -- 200 texts for $5/month. And I usually only used maybe half of that. Now the only messaging option available is the unlimited for 4 times that price. Not happy to say the least.