BASSA/CC89 is a branch and that means it is controlled (or supposed to be controlled) by Unite. BASSA does not have the power to authorise the calling of strike action. It is impotent, and especially so in the face of the many Unite VCC members.
BASSA/CC89 and Unite are separate entities and there is no automatic link between the two; Unite could terminate the arrangement as its discretion. It might just come to that!
Any cabin crew who remains a member of BASSA is not only wasting a not inconsiderable several hundred pound per annum, but is actively condoning this nonsense. Resign and join Unite directly, if you still feel you want to be a union member.