Iphone 4s keeps freezing in every setting so frustrating

Hi all, hope you can help, when I am using my iphone 4 keeps freezing in all settings, phone, contacts, recents etc...then in messages, what do I do? I've unfortunately already tried resetting it, with the on/off button at the top at the same time as the home button until the apple symbol shows up yet to no avail it simply starts up and does it again....as in if I go into messages, a whit blank screen appears and then after 10 or so minutes of going back and fourth the messages might come up, or my recent calls come up, however if I then hit the phone symbol in contacts to call someone, it does nothing...... very frustrating, has anyone had this happen? What do I do?