Oh how some are blinkered/biased in their comments
Three made the changes to the one plan a year ago and stated then that anyone already on it would have their contract terminated and offered a different one instead.
You have had about a year extra on it and you complain it was only announced last week. You need the data ? then go with BT mobile and use their unlimited wifi for your needs and you get a better coverage at the same time. Otherwise go look elsewhere for what you want, its a free market.
As to the merger I can see no difference between 2 big and 2 smaller companies or 3 big companies as far as competition is concerned, No way will EE and Vodafone increase prices in a big way if 3 are not as they would lose customers,