system Subscription mistake

Complement. I wish to complain that I did my December subscription 13/12/14 for my line 07086051616,i was given 2,500 min to make calls. I used only 560 min out of the 2,500 min. But my subscription was stopped on 19/12/14(seven days interval)  that I have exhausted my subscription for the month. Please I need an urgent Refund of my call min please.