What device are you using to watch the sports content?
Have a look at this thread, might give you some confirmation
@Gilliansing in the terms and conditions you'll see that it takes up to 10 days for the free pass to go active.
Secondly, the mobile pass only gives you access to 5 of the 11 sports channels - Premier League, NFL, Arena, Racing & News.
Lastly, the mobile pass will only work on a phone, not a tablet.
I've got the same issue. I bought mine on the 23rd of December. I have a running mobile pass which I cancelled (this pass will continue until the 19th of Jan). I was expecting the 4 months free pass to appear by now. I spoke to someone on chat today and they re-enabled my mobile pass and said to get back in touch if I get charged on the 19th! Confusing...