EE creates 300 jobs at Merthyr Tydfil, Darlington and Tyneside
Up to 200 jobs are being created by mobile phone company EE at its call centre in south Wales with another 100 in north east England.
Customer services and sales jobs will be based at Merthyr Tydfil as well as Darlington and North Tyneside.
A total of 15 apprenticeships are also being offered in south Wales in a link up with College Merthyr Tydfil.
Merthyr Tydfil and Rhymney MP Dai Havard said the decision was a "vote of confidence" in the local community.
The Labour MP added: "EE knows that Merthyr Tydfil is a place of opportunity and I am pleased to work with them to build our digital economy."
EE, owner of Orange and T-Mobile, provides mobile and broadband services and has over 15,000 employees and 27m customers.
It was also the first to offer a 4G network in the UK which provided increased broadband speed.
Assembly member Huw Lewis praised the company's commitment to create the 15 new apprenticeships in November on top of 25 due to start soon.
"I was pleased to visit the EE customer centre here in Merthyr Tydfil recently and to meet with 12 of the new apprentices who were all incredibly enthusiastic about working for the company," he said.
"Today's announcement of additional jobs is a welcome boost for Merthyr Tydfil and a sign of the confidence EE rightly has in its Merthyr workforce."
Recruitment starts this month.
Dr Kath Ringwald, from the business school at the University of South Wales, told BBC Radio Wales an influx of 200 jobs was always extremely welcome, especially in an area like Merthyr Tydfil where there is a high level of unemployment.
She said call centres make a significant contribution to the Welsh economy.
"The significance of the apprenticeships is that it signifies that these are jobs that are going to endure and go on in the longer term and will offer some good training and security in the longer term," she said.
Francoise Clemes, EE's chief of customer service, said the town was already home to one of its customer centres and would be good news for local job-seekers.
"As well as providing a much-needed jobs boost for an area which has been badly hit by the downturn, the increase in employees at our customer centres reinforces our commitment to providing the best service possible to all EE customers," she said.