IPhone 4s won't send message to one person all of a sudden?

I was messaging someone who uses an iphone 3GS. I sent a lot of messages over the space of 30 minutes as well as calling the same number. I then proceeded to send another message after the call, and it won't send. "Not Delivered" pops up at the bottom of the message.
My service is fine.
I know that the person has turned their phone off, would this stop the message from sending? Or is there a limit to how many/how long the messages can be? It is a pretty long message, but I have sent long ones before. I tried shortening it, I tried removing the capitals from my overly excited exclamations. I tried restarting the phone too. It isn't an iMessage either, just a normal SMS.

How to find my lost iphone 4? - 1

I lost my iphone and I want to know if I can find it anyway. I've tried to find it by 'Find my Iphone' but didn't work. Does anybody know other ways to find it? Please tell me.

How to fix my lock button on my iPhone? - 2

I dropped my phone in a tad bit of water yesterday and I was having problems with it of course. I had it sitting in rice all day and night. Now, the only thing wrong is the lock button is like jammed and it randomly every second or asks to it off. It's starting to get on my nerves and I'm about to throw my phone at the wall.

How come this song won't load on my iphone?

I downloaded Suit and Tie off the Internet(I'm not paying a ridiculous iTunes price) but it won't load on my iphone. Yes I did click the manually manage the music and videos thing and hit applied but still it won't work. I dragged it across but it won't show up on my phone. I don't want to sinc it because it screws up my iphone.

My Iphone earphones keep falling out when running?

I have the latest ipod headphones (the ones you get with the iphone 5) and they still always fall out when i run! It's so annoying and i don't want to get specialised earphones unless i really have to…
Does anyone else have this issue and how can i fix it?

My LED Flash light for my iPhone 4S is stuck ON

I put it in a water proof case today and i noticed a bit of water got through, at first the sound didn't work and it wouldn't charge but i fixed that, and now the flash is stuck on, even when i completely turn my phone off, and my phone won't connect to iTunes so I can't even restore it, I've tried everything:'

Can you flash an Iphone 5 from sprint to boost mobile?

My sisters birthday is coming in a few months, and I'm getting her an Iphone 5, but I have boost mobile. I know you can pay someone to unlock it or flash it. I just wanna know if after it's unlocked it'll be possible to connect to boost.