DDI stands for Direct Dial In, it's commonly used in telecommunications networks and systems to represent a telephone number in a range of numbers.
For example; 0207 4300 450 - 459 represents a block of 10 DDI numbers.
Sometimes we refer to SN-DDI numbers which is a Single Number DDI. This is a number which is not consecutive in the range and is typically unique on an ISDN circuit.
You can rent DDI numbers on typically any business grade telephone line like ISDN2e, ISDN30e and SIP Trunks.
Looking to purchase DDI numbers for your business, contact us!