Caller: 'Telstra Corporation'

Robocall advising that my internet was to be disconnected and I should 'press 1' to speak to a technician. Of course I didn't. But we've had a spate of these calls over the past fortnight. All from different numbers, some of which are 'disconnected' or incomplete' numbers, others which actually belong to a 'real' person who has just had the same call!? Using a real number to hop to the next number?