Straight Talk iPhone 5 can't receive calls/texts

iPhone 5 can't call/text or receive calls/texts. Straight talk is my carrier. I have had the phone since Christmas. It has worked perfectly all of this time. On June 27, I came home and the problems started. Can't call/text receive calls/texts. Can't get on the internet unless I connect to my router. Called straight talk and they rudely told me to just go outside when I wanted to make a call or text. Problems began to escalate. Phone wouldn't work outside my house or on my porch. It only works when I go very far from my house and even then it is testy. Now it won't connect to my router unless I'm right next to it. Called apple today and the support person had me update Network Settings. It worked! So excited, was able to make calls and text. Told the lady thank you and was thrilled that all seemed to be fixed. Set my phone down and came back to it in about five minutes. Guess what. It was having the same old problems again. Don't know what else to do. If I don't get any answers here. I suppose I'll call apple again. Hoping someone here is having the same problems and knows what is going on. Also, does anyone know what tower iPhone 5 uses with Straight Talk? I've heard it's Verizon, but I've also heard it's AT&T. Any help would be soooo much appreciated!