bb 9900 sos solution

hello there i have (2) BB-8520 and (1) BB-9700 having same kind of problem about sos call failed . firmware bb dakota 9900 i upgraded all of them by the latest operating system did the reset factory from JL_Cmder also , but still the problem is same initially signals appear but when i try to make any call it say's "call failed" then mobile goes to sos signals vanishes please help me out with it