Had a call from 6 different numbers over last few weeks. All have same first 6 digits - 0468 000, only the last 2 are different - 232, 866, 608, 613, 206, 082. My phone is identifing as suspected spam, so I don't answer. Asumming they are spam.

No message left, just silence on the line. Second call the following day from 0468 000 307, where the voicemail left was silence, followed by a ringtone, followed by someone saying hello... assuming it's a spam/call centre/autodialling.