Vodafone is a mess. I bought a 24Gb pre-paid sim which was supposed to last 2 years but they 'lost' my plan after 6months and 2Gb of data use. Spent an hour on chat with them telling me that no such plan had ever existed until I told them I had all the receipts and evidence of how much data I had used and threatened to take them to the small claims court with expenses at £60/hr for my time. They capitulated quickly after that and restored it, then 'lost' my plan again the next month.

I've had problems with billing glitches with four utility companies in the UK now and I am starting to suspect that overcharging people and hoping they don't notice is actually a common business strategy in the industry and if they get caught they blame bad IT but really their systems are configured to do this on purpose.