itunes isn't updating my iphone ios from 4.2.1 to 5.x
my phone model: MB489TU
SERİAL NR: 868448BLGY7H
IOS:4.2.1 (8C148)
No idea about 3G or 3GS
Why ios update isn't possible. Please help me to solve this problem.
Thanks
Ahmet T. Oner
iPhone 3G, iOS 4.2