Google Journey voices are the most natural-sounding option available — free, built into the phone line.

Easiest way — import your whole phonebook at once. On your phone, export all contacts to a .vcf file and drop it here — thousands import in one shot. (iPhone: Contacts app → share/export vCard. Android: Contacts → Settings → Export to .vcf.) Live-reading the phonebook mid-call isn't possible — sync it here once.

Or paste a few by hand (one per line — name and number):

Try a number you added above (rings through) and one you didn't (gets screened).