Dial-a-Disc was a music service run by the (then) General Post Office (GPO) where, by dialing 16 or 160 on your telephone, you could hear the latest hit records played down the phone line. Sounds primitive and it was
1. Second-hand shops. There was always one locally. You take your unwanted stuff along and the guy gives you cash for it (or offers to bin it for you).
Compare that with Ebay, almost a day's work and a fortnight's wait.
2. Anything analogue. Change TV channel in an instant!