My SIM card has only just been activated. Why did I already receive an invoice or payment invitation?

A Mobile Vikings subscription is a so-called 'prepaid - postpaid' subscription. With a traditional subscription, you pay for everything afterward. With Mobile Vikings, you pay partly in advance, and partly afterward.

So, what does that mean?
You always pay for your bundle in advance, just like with a prepaid SIM card that you top up in advance. That is why you'll receive your first invoice or payment invitation a few days after activating your SIM card.

Your usage out of bundle is paid afterward - postpaid. We can't charge this usage before it's happened. If you'd like, you can limit your out-of-bundle usage.