When you have a previous relationship with your client, it's important that this be reflected in the customer experience. Often, the data concerning the client is available in a separate system from your call center ACD software. Keeping data in a central location can be an effective way to ensure data stays in a consistent state, rather than being replicated and updated separately. It's important to make sure it's available when and where needed.
Having a robust IVR is key to handling your customers needs in an efficient manner.