Investigate the [customer's] situation. When the investigation will take longer, make a specific commitment to get back to the customer. When making commitments to call back it is important to give a specific time frame rather than telling the customer you will call back "as soon as possible" or "right away." Terms like these mean different things to different people. "Right away" might mean sometime today to you - it could mean within fifteen minutes to your customer.
- Renee Evenson, Customer Service Training 101