Charge for FaceTime and iMessage every time i reload my phone

Everytime i reload my phone pop-up window appears like "your carrier may charge for SMS messages used to activate FaceTime and iMessage" for the first time i chose ok it charged and then everything was ok.Then once my phone discharged i charged it and when it turned on this pop-up window appeared again , and every time i reload my phone it appears.What should i do? Thanks in advance :)