in the united states, do they sell the cellphones chip alone or it has to be with the cellphone?

Answer 1

I think you are refering to a sim card and I know that T-mobile sells them for $20 if you want there service but if the phone is from another provider you will need to get a sim unlock code from them and unlock your phone before it will work with a nother providor.

Answer 2

Yes they do sell.If you know how to fix in your old cellphone,you have to check it out first whether it is COMPATIBLE WITH YOUR MODEL OR NO? The chips and cell phone manufacturers are different.In US most of the chips is manufactured by Texas Instruments and cell phone is manufactured by Motorola.Some they get manufactured with Intel,AMD and others.