Re: Business hours keep changing from clossed to open
Unfortunately, at this time there is no check box to note that your hours are "by appointment". The best recommendation is to make it highly visible on your website so your visitors will know your process. Please be assured that this recommendation has been a subject of various other threads such as this, acknowledged by Google Community Manager, Liz.
I'd also suggest reading this help section on setting hours, and depending on your business model, possibly setting hours that accurately reflect your 'customer-facing' hours.