I have raised this issue before both by voice and by Web email.
There is inconsistency about display when one checks Usage to date.
I like to minitor my usage to try to avoid exceeding my Plan limit.
Yesterday (19 June) I selected Filter Data -All.
The option to Download Usage was displayed so I downloaded in CSV format.
Today that option to download is not displayed.
Your Help Screen tells us the steps to check usage including Select the Download Usage Tab.
Can Vodafone please test to ensure that the Download Option is always available.