Credit that works against me

<p>I was credited back R275.00 into my moderm sim card, which I want to buy data with next month, but now I can't use my moderm cause as soon as I insert it all the airtime will be used although I already bought data for this month, I was told that I cant transfer it out so that means I will lose all that air time that was credited back to me, this is very dissapointing cause now I'm stuck</p>