无法更改项目中的包ID，显示为灰色

I'm having a problem with bundle identifiers. In the Summary section of my project in Xcode and under 'Identifiers', I can't seem to change the name of my bundle ID as it is greyed out. For example, my project name is 'My App'. In the identifier text box in Summary, it says this 'My-App' and is greyed out. However, my bundle id in my provisioning profile is this, 'com.mycompany.myapp'. I would like to change my bundle ID in my project to that but I can't seem to be able to. Any ideas why it is greyed out? Thanks!I'm having a problem with bundle identifiers. I