Hello Bram,
We could do this, but there might be duplicates in the list: if you move (keeping your number) from operator X to Mobile Vikings, then to operator Y and then back to Mobile Vikings, you would have two "subscriptions" in our system, and both would have the same MSISDN.
In fact, there is no need for separate referral links anymore. Referral links are only linked to the referring (existing) user, so it does not matter which link you pick (as you might have noticed on
becomeviking.com: there it is just the first link in the list). In the past there was a link to the referring subscription with plans to add extra functionality to them, but this idea was abandoned.
So if you are showing these list to an end user and wondering what would be the best way to do it: don't fret about it, just pick one, they're all equal.
Jan