"On" is more often used to describe someone who is in the process of taking part in a call more generally. "Will you be on that call this afternoon?". But you could equally say "in" here. The phrase "on a call" can also mean making a visit, usually an official one.
Also asked, is it rude to call?
Talking on the phone, of course, used to be the primary source of communication. In addition, not picking up the phone was considered rude and impolite, however, now with the explosion of texts and email communication, calling on the phone is considered rude and intrusive. 27 percent of adults have no landline phone.
Additionally, can we schedule a call?
Call Planner is an app for Android that lets you quickly and easily schedule a phone call or create a list of calls to be handled. The app has the ability to schedule recurring calls such as daily, weekly or monthly so that you don't forget to make that important call.
Is it rude to ignore a call?
When someone calls you, it disrupts whatever you're working on. Phone calls take control away from you and give it to the person calling. So when they don't answer your call, it's not because they're trying to be rude. It's because they want to keep things under their control and make the most out of their day.
Can we have a call when you are free?
Yes. That is a grammatically correct phrase. The phrase "Call me when you are available to talk" implies that you want someone to call you once their situation allows it. The wording sounds a bit formal, but it would be acceptable in just about any situation.