The stock of Bellevue-based T-Mobile US rose 5.5 percent Friday following a report that SoftBank would be willing to give up control of Sprint if it would help cement a potential merger of the two mobile-phone carriers. The stock of Bellevue-based T-Mobile US rose 5.5 percent Friday following a report that SoftBank Group would be willing to give up control of Sprint if it would help cement a potential merger of the two mobile-phone carriers.