meg your day

i dont understand how you can offer customers meg your day offers but eat up the customers data and airtime instead of using the data offered to them.

for example today, meg your day is 1 gig facebook data till 12 midnight tonight. but i went onto facebook today for less than half an hour but i see all my airtime is finished, so is my data and the 1 gig meg your day given to me. how is this possible. this is the second time this has happened. why give customers the offer and then use up all their existing airtime and data. i have all the sms's since this morning to confirm. all i did was watch a few videos on facebook but R100 airtime is gone and 230 meg data is gone, including the 1 gig meg your day, how is this possible, i ask with tears in my eyes.

please advise.