IPhone won't send pictures to non iPhone users?

I have had an iPhone 4s for about a year. Just within the past couple of months I have not been able to send or receive pictures from people who don't have iPhones. I have tried sending pictures to different people who have different phone and different service providers but nothing works. I don't think it is the plan I have because I have an unlimited date package and my fiance, who is on the same plan doesn't seem to have this issue. I have looked around on the internet with other people who are having the same problems. I have checked all my settings, deleted any camera apps besides the one that came on the phone and have reset the network setting. It still will not work. I have updated my system to iOs 6 thinking that was the problem of a new update coming out, but there still is the issue. Is anyone else having this problem and what did you do to solve the issue.

Added (1). I did what she said and my cellular is on, so that is not the issue.

Go to settings > general > cellular > and make sure cellular data is turned on

Andrea pretty much said it. You can't send picture to non iPhones over Wi-Fi.

I can't send pictures over Verizon 3g or wi-fi to non-iphone users even though I have unlimited data, have data on, and have disconnected and reconnected from the network repeatedly. Never had this problem with a non-iphone or on tmobile.

My daughter is having this problem with Tmobile

  • Why won't my iPhone send messages to non-iPhone users? I've had my iPhone 4 for a while now, I go through Virgin Mobile. I've never had problems until recently, but it's really strange. I can text certain people with non-iPhones, but some I get an error. I can receive theirs always. Any resolutions? I have changed the contact from iPhone to just mobile… Still doesn't do the trick. I have turned off MMS. No such luck.
  • Why can't my iPhone 4S send pictures to noniphone users? I can send pictures to people with iPhones, but I can't send pictures to people without iPhones, such as droids. This Is really frustrating and my mms, SMS, and cellular data are all turned on. I just can't figure it out.
  • Why can't I send pictures to non-iphones? I have the iphone 5s and ios 7. I tried sending pictures to my friends who don't have iphones but I just get an error message. But when I send pictures to iphones using imessage, I'm able to send pictures just fine. Can anyone tell me how to fix this problem?
  • Why can't I send pics or videos to non iphone users? I have a IPhone 5s and I can't send pictures to anyone that doesn't use imessage, why is this and is there anyway to set my phone to send pics to all phones and not just imessage users?