Call the owner or manager and be specific. Keep notes about your complaint so you can describe exactly what's been going on and for how long. Remember, good home care
companies want to hear complaints. If no one says anything, they can't get rid of a person they want to fire because they don't have the evidence. And chances are that if you have a complaint about an aide, they've had prior complaints as well.
Sometimes the older adult gets attached to a caregiver, doesn't want to hurt that person's feelings, and so doesn't want to complain. But you have to balance your desire to be a nice person with the fact that you're paying good money for someone to provide a service for you.
Sometimes families have a concern but aren't sure there's a problem, such as when items are missing but they don't know if the caregiver took them or Mom just misplaced them. In this case, think of it as reporting rather than complaining; you're just calling to report a concern. Start by saying you're really not sure if there's a problem, but you thought you'd let them know what happened. If the older adult is beginning to have more severe memory issues, this is something you'd tell the agency anyhow. You're a team; raising any concerns you have allows the agency you're working with to help resolve them.