I m an i card subscriber

I m an i card subscriber n i got a msg sayin that i have to finish my sms dedicated balance by 29th august.I ve around 1000 in my sms balance.Wen i got d chip it was valid for a year n now company wants me to finish my balance in 3 days.If i would ve known tat they ve such a scheme i would not ve got tis scheme ,i would ve prefered some other.May i knw why such a msg has been send.Why do v ve to finish it in 3 dys which otherwise for meant for a year….