I have just found that Vodafone has halved the amount of data allocated to my connection because the have removed the account type that I have been on for the last two or three years. I used to be on 20Gb during peak hours, plus 20Gb for off-peak. Now I have limit of 20Gb in total, regardless of time of day, and have been subject to a fair use policy which they reduce your speed if you download more than 2Gb in one day.
I have made three calls to them, and I am still waiting for a manager to get back to me.
I think this is a very poor level of service.