Complex sentence: The radio show often featured a phone call, or appearance by Noel Gallagher of Oasis, or other celebrities, and discussions revolving around listeners' emails, text messages or phone calls.
Split into simpler sentences: The radio show often featured a phone call to, or appearance by, Noel Gallagher of Oasis. Other celebrities also frequently featured, and there were discussions revolving around listeners' emails, text messages or phone calls.