Hopefully you come back to get some help. Along with B. Diddy's questions I have one, is this an unlocked device?
In my experience with unlocked devices and SMS issues, I've always turned to my carrier. On two occasions they've told me that they had to restart something on my account and just like that my SMS works both ways. I have Verizon and you have Straight Talk but I wouldn't imagine they would be so different. So if they aren't being helpful you might just mention to whomever you talk to that, "last time this happened they said they had to restart my SMS service". Not the total truth but if it isn't working and they aren't helping it can't hurt to sway them just to try.