How can we talk to a care manager?

Gently and professionally. Try as hard as you can NOT to develop an adversarial relationship. They lead nowhere fast. Have a diary of your information at your fingertips. Start with "I hope you can help us; we are not certain where we can turn". This is instantly assuming they are there to help and you are throwing yourself on their mercy. It's a place to start. Tell the person you understand that any complaint is more or less a he-said-she-said thing, and that there will be need time to investigate, and you can appreciate that; that you ask only to be updated that they are working on things.