Being charged $0.00 over a year after leaving Vodafone

Yesterday I recieved an email from Vodafone with an attached invoice for $0.00. I left Vodafone well over a year ago and then suddenly they send me a bill for nothing. But wait there is more, if I don't pay said $0.00 by the 17 January 2019 I will be charged a late payment fee of $18.40 and no doubt my credit score will be affected.

Why do Telcos and in particular Vodafone have so much issue with billing is it really that hard?

@JasonParis

@MikeHales

I have no desire to wait an eternity on the phone trying to get this sorted could either of you get this looked at I will PM my OLD account details when one of you replies.

Thanks in advance