Thanks IndianMascot. It looks like the mistake is on my side. I should've opted out for email for communication. As I selected mobile, there may be an issue sending the PIN to my mobile.
Again, I created another login (with email as preferred channel for communication). But this time, it looks like there is an issue on their side as my MDN seems to be already registered. 🙂
I tried to delete my MDN from the previous login. It didn't budge. 🙂
Anyway, I appreciate your help on this. It was entirely my mistake when I created my first login that I didn't select email.