Just found this thread after having received a text message from FlightClaim as well. Contrary to most, I have flown with WizzAir (from Luton/LTN) last week and received the same text.
I haven’t flown with BA for 5 months. It’s possible that my number might have been part of an earlier leak, however the timing is in favor of WizzAir. It makes me think the problem may be larger than anticipated.