Q: my iphone4 suddenly went off and whe i turned it off and back on its asking me to activate my phone but iam unable to activate my iphone. its showing me as activation error

the error says, 'activation could not be performed. try again later or contact customer care'

i tried following those steps couple of times but still the issue could not be solved

its locked to a service provider. i tried restoring it in a recovery mode but still the issue remains the same. I went to apple store and even they couldnt come to a conclusion as to what it is the issue.so they suggested me to replace the device.