The expansion, backed with almost pounds 900,000 from the Department of Trade and Industry, takes to 3,100 the number of call-centre posts created by the group since January.
Bob Fuller, chief operating officer, said: "The market is expected to expand significantly this Christmas, creating further demand."
The pounds 8m Plymouth call centre is scheduled to be operational in August 2000.
Orange shares ended 22p stronger yesterday at 1,132p.
Separately, Express Dairies, said yesterday it was shedding 190 jobs with the closure of its plant in Salisbury, Wiltshire. The dairy, acquired four months ago when the company bought Glanbia's liquid-milk operations for pounds 100m, will be shut by mid-December. Express, which has already unveiled plans to axe 400 ex-Glanbia jobs with closures in Birmingham and Manchester, said it will transfer the plant production to London and Sussex.
Express Dairy shares eased 1.5p to 127.5p.