I got my first follow-up email after applying. Rather than asking about my availability, the recruiter said he'd call me on my mobile the next day, sometime late morning to early afternoon, over WhatsApp. I replied explaining I wasn't free that day and offered a few alternative time slots — but haven't heard anything since. Felt like pretty unprofessional way to arrange an interview. Atleast be clear about what time you are going to schedule the call. Time is precious for everyone.