unlimited data not working

Hello, I have added O2 unlimited month to my contract mobile S on 26th of june, currently in this month of june, it consumed all my 8GB data and now mobile data is showing completed but its not going to the unlimited pack, and am currently unable to use data. I have expiry for this unlimited pack till 26.07 but I cant use anything right now. It would be great if you could help me out.