My iPhone 6 suddenly deactivated

My iPhone 6 has suddenly deactivated and I cannot get it into it. When I turn it on and enter the correct PIN the following message comes up...."Activation Error....Activation request could not be completed. Please press the home button to try again. If the problem persists , please contact customer care.”

Can you provide information on how to reactivate the telephone without losing existing information stored on the iphone. Thank you!