I joined spotify paying £5 a month for premium with my student card. For the first month atleast this is what I was charged but I've just looked at my bank statement and with no warning it's gone up to £9.99.
Hi, are you sure you are being charged for the same account, and are you sure the NUS card didn't expire?
If you go to http://spotify.com/nus and resubscribe, does it work?
If not, then you should use the Support Form to contact customer services.