Unless of course the OP is trying to send pictures using iMessage which is clearly what the OP is intending. These messages use your data allowance or Wi-fi and are not generally chargeable.
@Pinghind couple of things to check. When you receive a normal text message from the person you are trying to send pictures to is it green or blue? If it’s going over iMessage it should be blue. Also check in settings/messages and make sure iMessage is turned on on both phones and that your phone numbers are showing up correctly in the send and receive section
