Ok, so I called Telecom, and there was an overdue amount, I simply underpaid the last bill, totally my fault. It turns out the MyTelecom page doesn't actually show this clearly (and the guy I spoke to said several people had raised this to 128, and that they would be putting a request through to the MyTelecom team to see if a change could be made to the page to make it clearer about any overdue amounts).

So now I feel stupid for having an overdue amount and the world knowing about it! Thanks to all.