How can the Internet work with a negative balance?

Question

MTS

Mother brought an MTS 3G modem from work, which had not been used for a long time due to an allegedly zero balance.
I connected it, checked the balance, and went nuts, because in response I received an SMS of the following content

Balance
  07-09-2014 17:01:08

Минус:475000,80р,Лимит:2870000р

At the same time, the Internet connects and works, at a good speed (about 2 Mbit / s).
Well, that's actually the question, how is this even possible, and how safe is it to use this Internet (in terms of the sudden appearance on the doorstep of a couple of strong guys with bats and a strong desire to get these 475 thousand)?

Answer 1

corp connection, it can work like this, but to issue you an invoice here you need to look from the legal side and know all the details of the connection

Answer 2

Most likely a corporate rate.
They are usually brought to the whole company in one pool, with a postpaid settlement system (and even after a few months, so that the accounting department has time). As a result, on all corporate SIM cards in large companies, the balance is usually minus several million.
Your 475kr is 200-300 people with a payment delay of 2-3 months for one legal entity. face.