Q: i cant update  my phone coz showing old apple id, i already change my id and password

You need to delete and redownload all the applications associated with the old Apple ID. This may require repurchasing paid ones.

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Click here and follow the instructions.

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Before deleting everything. Try signing out of iTunes&AppStore on device. settings>iTunes&AppStore> tap appleID> sign out> sign in with new email address

If you have created a new appleID> delete apps and download under new appleID

Did you update your old AppleID or did you create a new AppleID?