Prepaid unlimited texts, verification SMS codes

I'm on the unlimited prepaid plan$65 with auto pay, I'm supposed to have unlimited texting but today I downloaded an app and when I went to receive my verification SMS codes I was notifiedmy quata had been met, at that time I realized all my texts coming in on network were not making it to me only text on apps that provide their own free texting. Why is this happening? I'm paid up on account, I owe no money and as far as I can see I should be recieving my SMS. Can anyone help me work this out?