How to make old people's mobile phones unable to make or receive calls?

Hello, according to your description, if the mobile phone card and network problems are ruled out, I have the simplest way to help you solve them. You should back up your important SMS and phone number in advance, and there are factory settings in the phone settings. You should enter the password. If it has not been modified by itself, the passwords that come with the factory are all 4 digits, such as1122 0001234. Thank you.