The number since I got to HK many years ago successfully ported over to SoSIM this morning without any issues, and SmarTone's online system has already removed the number from their systems (my wife is still using the same SmarTone plan - for now). I stuck with SmarTone for way too many years paying ~250HKD a month for 5GB + Fair Use unlimited but lower-priority fast enough for me mobile data.
I hope others have success switching to SoSIM if they'd like.
Within the SoSim app, I also see an option for 88HKD for 90 days of 120GB FUP and 10,000 minutes. Does anyone know if you can just buy that 90 day 120GB plan and not the base 33HKD 30-day 50GB plan?