Samsung Rugby III

I purchased a Samsung Rugby III almost two weeks ago and while I really enjoy this phone, there is one problem I am experiencing with it. All of my contacts are saved on my SIM card and when I go to edit a number on the SIM card and I erase the number, the phone freezes, the screen turns off, then comes back on, automatically adjusting the brightness to a higher setting, while still frozen, then reboots by itself. Sometimes it shuts itself off. I have replaced this phone once already at an AT&T store and I have done an online chat with a Samsung employee. I think there is a problem with the SIM card or the operating system on the phone. When I copied a contact to my phone and made the changes there, the phone was fine. It does this fre...
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