OTP Issue after porting in?

Thinking to port over from M1 Sim Data to something else after getting fed-up with the slowed down experience (I felt that and it has been getting obvious) for the past few weeks, VIVIFI being affordable and is under Singtel, it's no doubt a better choice for trial and error to see if Provider's brand does make a difference.

However, I came across some users' reviews on Google, alleged they are having OTP issues right now which are yet to resolve. This apparently messed up their access to banking apps and some other websites using OTP.

Anyone has/had this problem while porting in? Any user experience to share will be greatly appreciated. :)