You are not allowed to call off.  Reschedule your appointment for after work.  Thank you, management.

The rule at our store is you must speak with the store manager or co manager for a call-in/off.

See if you can pick up those lost hours another day.

I suppose you could speak to your department manager to give them a heads up so they can find a replacement for you since the manager probably won't relay the message.  Or arrange for someone to switch shifts with you or come in later for your shift?

But, definitely speak to your store manager.

You need to use a sick day, so don't feel guilty for using it. 

For a dr. appointment you should have scheduled it through the greatpeople.me website, since most are given to you weeks ahead of time. Calling off for a non-emergency is very bad form.

in any case you call the store, speak to the manager, and tell them you will be unable to come into work that day and remember to tell them that you are sorry for the inconvenience. You do not, legally, have to give any other explanation if you don't want to. Several hours advance notice is also a normal requirement.