pay back my money

on Tuesday I went to checkers pineslopes in Fourways to send money via money market. On Wednesday when my younger sister went to fetch the money she was told there was NO MONEY on the numbers I gave her. This is not the first it happened to me and the first time I let it go but this time I will not, and the same checkers Pineslopes. Please checkers advise how does this happen and I will appreciate it if you could refund me my money and I will never ever use your store any more.