How should I call a store about an employee?

I want to go to a store to return things but I do not want to encounter this one employee who is usually at customer service. I haven't seen her for a while not but I don't want to take the chance. Should I call before I go to the store tomorrow and ask whether she will be in today? I know her first name. How can I call the store and ask about her without making it seem like I'm trying to avoid her?