I had a similar issue. I got the email through on my upgrade program saying I was eligible to upgrade, only 15 quid a month will be added to your bill, so I thought sod that I'm not paying 15 quid a month more. Only to find that when I went to the upgrade lounge it was only actually £7 more, but by the time I'd visited the upgrade lounge to check, the £100 discount had gone, as had the free buds 2. So now I'm just waiting, if no good deals come in the next 3 month of my upgrade window, it looks like I'm stuck with the 4.