Problems with MMS since 6.1 upgrade on Iphone 4?

I just got a Iphone 4 for Christmas… I have been able sen and get Pictures no problem but i upgraded from a 6.0 to 6.1 a few days ago and now i can't get or sent pictures all the time.

Sometimes i get some other times i don't

I have reset the phone and the internet settings and still nothing
i try to send a picture and i get a red! And couldn't deliver ( i'm sending it to other iphones)

what's going on?

Is your cellular data turned on? You can't send or receive picture messages unless its turned on, even if youre on Wi-Fi.