How many times should you call back a hiring manager?

So I was out yesterday visiting family at some campgrounds all day. My phone had died and by the time I got home it was 9pm. Which is too late to be calling someone back.
I was called by the hiring manager of a job I'm trying to get at 1:30pm yesterday. I wanted to be polite so I waited till 9am today to call her back.... No answer and it doesn't give the option to leave voicemail. Just says shes unavailable.
So I waited half an hour to call again... So at 9:30am i called, went straight to the unavailable message with no rings...
So then my partner said. Wait 5 mins maybe she was on a call.
So 9:35am i call again, it rings, no answer.
How long should I wait before calling again, and how many times should I try and call this woman?
I really don't want to come off as an annoying pest to her, which is why I'm asking this

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