You can't send SMS over 4G, or MMS, or both? My SMS works fine on 4G. Those send over 1x, so 4G shouldn't matter. I tried sending an MMS yesterday over 4G in Schaumburg, and it didn't send. I had to switch to 3G to send it. Which ROM are you using? I'm using CM10. I had assumed it may have been a bug in the ROM.