Rain billing

Hi I'm having issues which i dont understand with rain the last time i used rain was January which was supposed to debit at the 1st of February and the transaction was unsuccessful but now on the 1st of march i made payment of R250 so it stated im still owing so i was checking my February statement it states that i am owing R500 instead of the R250 for January February was charged but i didn't use rain since my simcard is only active when i used so i called rain and they told me its unlimited but on my statement it's written pay as you use and the February data usage was 0 but it was charged R250 .