I can't receive SMS when I have low storage
SMS, etc. are stored on internal storage.  If it's getting full, then you'll have to uninstall some apps to free up space to receive more messages.  Not much else you can do about this.

My suggestion, however, is that you use an app like SMS Backup+ to backup your old SMS messages to a label in gmail.  Then you can delete old threads which will free up space AND you'll still have a copy of all of your messages.