I usually text to see if it is a good time to call, as the younger generation don't seem to like actual calls, and I agree with them that they can be intrusive at times.
My daughter and I WhatsApp most days, and if it gets into a back and forth conversation I prefer to speak. Sometimes I just want to hear her voice, and she's happy to oblige - particularly now, when we haven't seen one another for ages.
My son is less communicative (by a long way!), but we both know that if the other calls and we are busy, we can just say so, and call back later, with no offence taken.
My mum rarely calls me, or her grandchildren, as she says she is worried in case we are busy. We have all said a hundred times that if she calls at a time when the young ones are busy they wouldn't pick up, but would call her back (I would always answer her, in the unlikely event that she called!), but she doesn't listen. She expects everyone to call her every time, and gets upset if we don't do it for a while.
I think one of the problems is that all of us keep different hours, so our 'downtime' happens at different times of the day. Mum is an early bird who goes to bed just as I am sitting down to relax for the night, I get up after she's been up for hours and stay up late, and the young ones are busy working and looking after children.