Master-Reset: all personal data will be deleted *2767*3855#
Hard reset is normally just pulling the battery out with the phone turned on. That normally fixes any weird glitches. But if you have used to much memory or did physical damage to the phone just pulling the battery will not help.
you are going to have to find your security settings and go in there and do a master reset. Try going into settings then reset settings but keep in mind anything that you have saved to the handset memory will be cleaned off. However this will not effect anything saved to your sim or memory card. I would back up my information to my sim or computer (sim you really can only save your contacts)
For this problem contact the service provider......