Premium-rate telephone numbers are a great tool to use for businesses providing a specific high-value service over the phone, where they require callers to be charged at a higher rate than that of normal numbers.
Because part of the call charge is paid to the service provider (you!), your business can be funded via the calls. A great example would be a technical support line that offers high value services that couldn't be billed any other way. In many cases, they are to cover their costs on a case by case basis rather than charging customers continually for a service they may never use.
These Premium rate numbers are not just solely used for companies wishing to generate revenue. They are also used by charities for fundraising, providing a quick and simple method for donating money.