Can receive iMessages, but I can't send them?

I have and old iPhone 4 and when I text other people with an iPhone, I would receive iMessages but I can't seem to send any. It would show that I have received and iMessage, but for some reason it sends a regular text message. I can still communicate fine, it's just faster through iMessage and I prefer it. Help?

Anyone know a good social networking app?

Not like Facebook or Twitter or that stuff. But a social app that allows you to make an avatar that looks like you, and can explore places. And meet new ppl ( other avatar ppl). Anyone know one? On iPhone. I found one called "Mixr". Idk how close it comes to what I want. Bc it won't connect right. But anyone know any good ones?

How to stop Verizon family tracker?

My parents put the Verizon family locator on my phone. I have an iPhone 5. If I turn my location services off and all my
Privacy settings on will it still be able to find me? If not then what can I do to make it not be able to find me?

Should i get the lastest iPhone 5 or galaxy s3 mini?

I am 16, i have a iphone 4s. It isnt that great actually not many things you can do with the phone. I am going to ask for a new phone. I was planning on getting the galaxy s3 but got the 4 instead. I dont like the s4 because it is way too big i dont want a mini tablet i want a phone. So what should i get. Which one is better and why.

Why can't I send texts from my iphone!

Alright so I have an iphone 4 with the latest version of iOS downloaded. I try to send an sms text and it keeps saying not delivered in red.iMessage is on I reset my phone already and my number is correct where it says "my number" help please any tips are helpful!

How to get songs off my old ipod onto my iphone?

I have a really old ipod and I would really like to get all of my songs on to my iphone 5 but when I plug in my ipod it does not recognize it on my computer. How can I get the songs onto my iphone?