I discovered another reason to avoid SMS OTP: I am currently visiting India and I have put my phone in Airplane mode because my Canadian phone company , Rogers,charges $15 per day for roaming and it is simply cheaper to buy an Indian SIM card and use it on an old phone to act as a wifi hotspot for my actual phone. So while my phone is in Airplane mode, I am unable to use my RBC Visa or MasterCard for any online purchases in India as there is no way for me to get the SMS OTP without paying Rogers the CA$15 .