I have an iphone 4. I have picture text for free with my plan, but am unable receive them. I believe that I have to have my data turned on to receive them, if I do that will I be charged for turning on my data?
You won't be charged for data used to send or receive picture messages (mms), however you will be charged for anything that syncs/updates/notifies in the background when you turn data on. To minimize this cost turn on data when you want to revive a picture message and then turn it immediately off after it downloads to your device. There is no way around being charged a little bit fir background data when turning on your data connection on a stock iPhone & can only be set up to only allow data for the transfer of pictures with nothing else accessing it is if you jailbreak your iPhone.
Also when you turn on data to accept a photo first close all apps to also help minimize background data transfer.