my iphone show alert :apple id is not existed

Not existed or disabled? See if anything here helps.

If this is in the iTunes/App Store, see the 3rd link.

If your Apple ID is locked or disabled - Apple Support.       

If you have changed your ID or password, have you followed the steps in this article?

What to do after you change your Apple ID or password - Apple Support.      

If you see a message that says 'Your account has been disabled in the App Store and iTunes' - Apple Support.    

If necessary, contact iTunes Support for assistance. See the Apple Support articles below for contact information.   

iTunes Support – world wide 

Apple Support schedule phone call       

If necessary, try Twitter

https://twitter.com/AppleSupport.          People have posted it may take an hour or more to get a response.

I have not seen a definitive solution for your problem. So, I suggest you use my search link in trying to solve your problem: apple id does not exist. You will see a number of links that are, or may be, related to your specific problem. 

If you want to contact Apple Support to deal with your problem, see:

Get a call from Apple support to help solve your problem using this link https://getsupport.apple.com/?caller=kbase&PGF=PGF63005&category_id=SC0245&symptom_id=23362 Be patient. Sometime this site is not fully functional.

Apple ID Support https://support.apple.com/apple-id

Apple Support Twitter https://twitter.com/AppleSupport  There may be a wait of an hour or so.

Apple ID account security for country-specific and region-specific help https://support.apple.com/en-us/HT204169

Get Support: We’re here to help https://getsupport.apple.com/. Go through the options to find the best one.