I totally agree and was caught in a very similar way to you. I have the dongle for occasional emergency use, and this was the reason I bought it.
I, too, clearly didn't use it over the period where the pop up announcement was active. Clearly Vodafone did not make every effort to contact customers. Like yours, my dongle was registered online. There is an email address associated with that - how hard would it have been to send an email to those customers effected?
And while most T&Cs allow price changes etc this is far more fudamental that that. The whole selling point about this dongle was that it was sold on the basis that the data credit did not expire each month. Removing that option is hardly a price tweak, it is a fundamental change to the product.
Now of course, like many large companies, Vodafone have decided they don't want to honour this and have just treated customers as valueless. When I called to find out why this device did not work I was told that I WAS informed and there was nothing I could do about it so pay up or cancel.
Given this device was not on sale for long before withdrawal, there can't be a vast number still in use compared with sales since.
If credit is purchased why does it matter to Vodafone when it's used?
If you liken data credit to petrol in a car - both needed to make it 'go'.... it is rather like filling a tank of petrol but if you don't use it within a month someone comes around and siphons it off so you have to buy it again.
Of course if that happened it would be regarded as stealing.......
