I've been stung by this as well. '3' are running a 12 month sim only contract with unlimited data for £17 a month though. The contract does lock you in but then at least you know how much your unlimited data is going to cost you from month to month.
If I had of known it was going to change I could of topped up 20 instead of 15 now it's going to cost me another 20 in a few days when internet runs out gg should send notifications about changes like this
giffgaff sent at least one email and one SMS to every member (you have to be opted in to receive info from giffgaff to get them). There was also an annoucement posted early in August, plus there was a big green banner across the top of the page every time you logged into your account, notifying the changes
I do not work for giffgaff, so cannot check anything on your account. This is a public community - please do not post any personal info.