Cell c enjoys freebies (Pay back the money!!)

I was using standard bank app to load airtime and entered my MTN number *** and amount R100. I thought I had chosen the correct service provider MTN but for some reason Cell C was chosen by default. When I bought the airtime, my account was deducted with R100 but since my number is an MTN one no credit was given on my number.I had thought naturally the system will pick this anormally and automatically refund me. I called my bank who advised that Cell C had already banked my R100. I called Cell C and spoke to a very arrogant Andiswa Keke..something(can't remember) who said it was my fault hence no refund.Even if it was my fault how do u justify banking my cash and with no corresponding airtime voucher? If u do an audit how do u justify an income where there is no corresponding service rendered?If I had entered a wrong cell c number and by chance recharged a cell c number for a magogo in Eastern cape I would feel grateful it was her early Xmas present, NOT when Cell C banks my cash without airtime voucher released. I negotiated for them to issue me with the cell C R100 voucher or refunfd me but Alas! They have already reported this in their profits, for what service really??