BlackBerry announced on Tuesday it will end its licensing agreement with T-Mobile when it expires on April 25th, meaning the fourth-largest carrier in the United States will soon no longer be able to sell BlackBerry products. In a press release, John Chen, BlackBerry's CEO, said although the two companies had "a positive relationship for many years," their strategies were "regretfully, at this time ... not complementary." The move comes after a lengthy spat between the two companies. In February, T-Mobile sent out promotional material to customers that offered discounts on the iPhone when upgrading from BlackBerry devices. Chen responded with a blog post, in which he said he was "outraged" by the "inappropriate and ill-conceived marketing promotion." T-Mobile responded by offering $250 to customers wanting to upgrade from an older model to a newer BlackBerry.