They usually seem to be invalid calls. Meaning they're asking for my address, or if the number they're calling is the address "XXX Melbourne Victoria". Sounds very shady to me. Parang they're marking a phone number and address, and seeing if there will be certain times when nobody picks up the phone, and possibly an opportunity para luoban ang bahay mo.
Are you aware if rampant ba ang scams that I think these guys are doing?