S4

I use the text messaging app textra and as of lately (few days), I receive many of my text messages exactly 15 minutes after my friends send them. I'm using the Samsung Galaxy S4 on Sprint. I tried turning my phone off and then on AND updating the PRL and profile, but none of them works.

I currently have a S3 and want to upgrade. Should I purchase the S5 OR S3?

My understanding was that Verizon uses CDMA, and CDMA phones don't need a SIM card to do voice, text and 3G. After I found out that the Verizon S4 uses a SIM card, I was somewhat confused. I did a little research and people said the SIM card was necessary for LTE data service. Learning that, I...