When I look at the "Recents"-tab on my iPhone 5, I can see about 100 call entries. But when I delete a call an older call moves up. So, older calls must be stored somewhere. Is there a way to recover the call history without deleting calls?
No, but you can log in to your cellular provider's website and see the call history for at least 18 months. Many carriers go beyond, some up to 6 years. Many providers have an app that contains this information also. And the carrier's info is much more detailed than the "recents" tab, including time, duration and cost. The purpose of the "recents" tab is not to provide a view into your history; rather, it is a shortcut for making callbacks.