The actress has been appearing in TV and print adverts for the mobile phone company in America since 2003, and has earned millions from the deal.
As to why she's been dropped by T-Mobile, the Wall Street Journal said that the communications giant wants to pursue a more "man on the street" style of advertising when it launches a new series of internet phone products aimed at luring customers away from other wireless and landline companies.
T-Mobile spokesman Peter Dobrow says, "When Catherine Zeta-Jones agreed to be our spokesperson four years ago, we could never have imagined the cache appeal she would have brought to T-Mobile. Her style, credibility and integrity have been a tremendous benefit for our company and our brand. We could not have asked for a better partner in launching T-Mobile than Catherine Zeta-Jones."