Been receiving unsolicited calls from a series of closely related numbers, no message, I haven't picked up.
They have the form (07) 3465 31xx
So far, (07) 3465 3164, 3169, 3171, 3172
My guess is that they are trying to get around their number being blocked.

I called back the number (07) 3465 3172 but was routed automatically to an ivr

tried to return this number's (07) 3465 3172 call but the line seemed disconnected

I returned a call from the number (07) 3465 3172 and spoke with someone who mentioned the company Clever Contacts

Someone in Clever Contacts called me once with this number (07) 3465 3172

called back this number (07) 3465 3172 but was routed to Clever Contacts voicemail

Got a call from Clever Contacts with this number (07) 3465 3172

I returned a call from (07) 3465 3172 but reached vm for Clever Contacts