Loss of Airtime because transaction wont be revers

I purchased airtime on my FNB banking app and accidentally typed in the last digit wrong. I have called both FNB and Vodacom and asked them to reverse the transaction as soon as I realised my mistake, which is something apparently neither of them do. This is a large sum of money which I cannot afford to lose. The number that I sent the airtime to is off and is not responding to my smses. <br> Customer service is lacking. I'm sure this is a mistake that many people make very often. <br> On a positive note - both call centre agents (although it took me over 5 minutes to speak to human being on Vodacom's side) were both very sympathetic but could not do something.