My iPhone 5 won't send picture messages?

I have had my iPhone 5 for a month now and only recently tried to send a picture to an android phone. However, when I try to send a picture message (MMS) it comes up undelivered.

I have reset my iPhone and tried switching mms off and on. I also turned my phone off and on when I first noticed the problem.

Does anybody know a solution?

I'm on o2, so unsure if I need to set MMS up on there…

Should I change my iPhone 5?

I'm going to the apple store because I'm having some problems with my MacBook but I also wanted to change my iPhone 5. I bought it in November and to be honest I wouldn't know if it had scratches or not, and now it has, although i always have a cover, but after a few weeks I noticed that my camera was not working properly: there's always a dark circle in every photo, you can't really notice it until you look for it but in pics where the background is white, it shows. Do you think this is enough to get a new one? I don't wanna look like I'm trying to "fool them" cause I'm really not, but I'd really want a new one, because of all the money I spent on it. What do you guys think?

My iPhone 4s camera stopped working?

Yesterday my camera was working completely fine, but out of nowhere it just stopped working? Now whenever I open my camera the screen is just black? Also, if I wanna take a pic on Instagram, it's the same deal with that. What should I do to fix it?

As of Jan 2013, is Siri available on the iPhone 4?

The most recent info I can find on this is that Siri is only available on iPhone 4 through jailbreak, but once done, you can't get to the Apple server. So no to Siri on iPhone 4. But all posts are a year or more old. Any positive updates here?

My home button on my iPhone 3g suddenly just stopped working?

I've tried restoring it, restoring it to backup, power on and off, etc and it still isn't working. It was working up until late at night last night out of nowhere. I'm not sure why it would do this. And my phone is jail broken by the way. What should I do? It's really annoying. :/

My iPhone don't connect to Wi-Fi anymore?

I have dropped my iPhone sometimes, is that why? When I try to connect the circle to the left just spins and spins and never really connects, even though I've got the right password. It only finds the Ip and the Subnet Mask, but not the rest… Help me please?

Should I buy an iPhone on a plan or should I pay for the full price upfront?

What are pros and cons?

To be honest I want to pay for it upfront because buying it on a plan feels like I'm just renting it. I want to feel like I actually own the phone.

But everyone in my family is on a plan and they say it's cheaper because they get free texts and stuff.

I don't know what to do? I know, first world problems but please help me. Plan or upfront?