Night express???Never selected

i have a Samsung S4 and i am using a prepaid sim card so i buy airtime and Data. i've been buying data for over a year now and all of a sudden theres a new thing called night express that gives you data that you can only use from 12:00pm to 06:00am. there was never a option to request night express when buying normal Data every month. MTN has told me that it is something i selected and they cannot take it off. i asked them how on earth can it be something i selected when buying DATA because i have never seen it before. this **** started a few weeks ago. i now have over 700mb of data that i cannot use because its night express. i need MTN to take the night express ******* off my phone so that i can use the DATA for my daily things. who in there right minds will buy night express? i sleep between 12:00pm & 06:00am. i have been to MTN twice and all they can say to me is that its night express which i dont want at all. i have never selected any option for this night express ******* and need it off my phone ASAP. i cannot sit with over 700mb of data that i cant use during the day. does MTN expect me to be up at night checking my e-mails etc. i am not the only person with this complaint.