Many cellular carriers will no longer support devices running on old software even if they are unlocked. The device has been tested and works great.
Apple iPhone 4S vs Nokia N8: What is the difference?
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Apple iPhone 4S vs Xiaomi Redmi 6A: What is the difference?
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Apple iPhone 4S vs Asus Zenfone 2 Laser (ZE500KL): What is the difference?
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iPhone 4s - Wikipedia
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