I do remember avoiding the phone calls from my mother. We were never close and, as she got older, she seemed so selfish and too demanding. She expected far too much from my siblings as well.
If I answered her call, it would be a two hour 'conversation' - well, being quizzed, really, about the children, my plans etc. then told about her many minor health problems - all with a heavy dose of criticism and complaints about everyone, including family members. It was very far from pleasant.
She got wise to my excuses e.g. 'There's somebody at the door' ('I'll hold') 'I have to go' ('No, don't you interrupt, I haven't finished speaking') and so on.
I think it was an 'ownership' thing - or 'control', as she felt entitled to disrupt my day, anytime, for no good reason.
(She had plenty of paid help at home, help from my siblings, I ordered her shopping, others regularly took her out etc. - there was really no good reason for it.)
Yes, I was busy, (very busy, early mornings, midnight marking) teaching and raising four kids, widowed and short of cash. There just wasn't any give and take with her - it was all take - and all so bloody negative and depressing.
So, I'd say, any contact, keep it short and sweet, keep it positive and interesting - maybe text or email rather than phone.