Why is it so difficult to send out the correct inv

I get my bill around the 14th of each month and most of the time it is correct.<br> This is however the 2nd month in the past year where it is an issue.<br> I received my bill, with April itemised calls. But the Tax Invoice is only up to April. Every time I phone the call center no one can give me a clear answer and when they email me my bill it is the same information.<br> <br> All I'm asking for is my April 2016 TAX invoice to be emailed to me. Simple.<br>