iPhone 4S only working when attached to mains charger after unlock

[Pittsy882]

I recently updated my iPhone 4S to an iPhone 5S. I paid to have my iPhone 4S unlocked and ordered a new sim card for my wife so she could use it. The phone is only accessible now when plugged into a mains charger, but remains on 85% charged and randomly reboots back to the apple logo.

Any ideas on how to fix this?

Thanks
Mike

 

[Highrisedrifter]

Hi and welcome to iMore.

I take it the phone isn't jailbroken? Have you tried a factory reset of the device through iTunes?