This feature cannot be provided from a PBX, however, there is a Digital Select Service that does offer this feature.
BT Presentation Number (PN) is a BT service that will allow customers to specify a telephone number for their Calling Line Identity (CLI) for outgoing calls, which may be different to the line telephone number.
The specified PN CLI will be displayed on the called persons Caller Display equipment if available, or used in conjunction with the 1471 service where calls terminate on analogue lines, to return calls to them.
Customers may require this because their business has separate incoming and outgoing lines for effective traffic management and resilience. Or perhaps, customers wish to direct return calls to a more appropriate number, for example a central help desk.
For full details of this service visit the BT Versatility Owners Manual