Why can't I send/receive photos via text message on my iPhone?

I have an iPhone 4S, which I bought unlocked and I use Straight Talk. I can't receive or send photos to contacts that don't have iPhones.

Can anyone tell me why this is, and help me get it working?

The first thing you should try to do is go to

Settings > Messaging > and see if MMS messaging is on or off make sure that it is on

another thing is do you have a data plan if you do then you are good to go im not to sure about if you dont have a data plan

the second step is go to

Settings > General > Cellular and make sure cellular data is on or off it should be on!

I have a iphone sean si from mexico buy i cant seand any massge to other phones i can resive but a cant seand

Answered my question!

Thanks, this fixed it for me too!