BT has announced plans to close 270 offices around the UK and set up strategic offices, including one in Cardiff .
The company said its "consolidation" plan is the biggest programme of its type in the UK.
There will be 30 strategic offices - with the first eight in Cardiff, Belfast, Birmingham, Bristol, Edinburgh, Ipswich (Adastral Park), London and Manchester.
They have described the offices as containing modern, future-fit buildings, including corporate offices, contact centres and specialist sites.
All eight locations will benefit from 5G coverage.
BT Group chief executive Philip Jansen said: "Revealing these eight locations is just the first step; we have dedicated teams working on identifying the best buildings to move into and which ones to redesign for the future.
"As a result of this programme, BT people will be housed in inspiring offices that are better for our business and better for our customers."
The consolidation effort, called "The Better Workplace Programme" by the firm, is the biggest of its type ever undertaken in the UK and is set to be finished in 2023.
The move comes a year after BT announced plans to cut around 12% of its workforce - approximately 13,000 jobs - over three years
Company officials hope that by slimming down management and reducing costs could save as much as £1.5billion.
Union officials said they had lots of answered questions remained.
Noel McClean, national officer of the Prospect union, said: "Moving from an estate of over 300 locations to around 30 by 2023 poses a huge logistical challenge for all concerned.
"For example, closing each existing building will require a period of consultation and considerable support for affected staff, from both the company and the union.
"While we are committed to working with BT to establish offices that are fit for the 21st century, what is left unsaid in today's announcement is what will happen to the current estate."
