Legal Question in Employment Law in California

Re: Sick Call

The employer is not entitled to know anything about your medical condition other than when you will be returning to work and whether the medical condition will impact your work upon your return. It might require a doctor's note after you're out for a time.

As to checking up on you, it's a nasty thing to do once you call in sick. People might turn their phones off to get some sleep if they're sick. Or, they might go to the doctor. Just because you might not answer the phone, it does not conclusively establish that you're malingering.