R50 off my Account each week

I have been an Absa client for many years now./ I get regular updates of my money in the Bank every Friday. I have however noticed that whenever I get these updates my money is R50.00 short (every week) SO if I have R300 on Monday, when I get my notification on Friday I only have R250.00. And if i dont withdraw any money I will have R200.00 the next Friday. I just want to know why this is??? Where does all the R50's go each week????? It would have been another case if this was happening and at the end of the year all the R50's are there for me to use but that is not the case. And if I dont have any money in my Account why is the R50's not deducted at all. Can someone please explain this to me as I dont understand it at all