consultant insist i am wrong and explaining to mag

I went to cna in mutual park to buy me airtime, at the till i ask the consultant (sazy tima ) for 3x R10 cellc airtime (me knowing that one R30 cellc voucher does not exist) .... he repeats to me by summing it up R30? I say yes cellc .... the consultant prints one R30 mtn voucher.... already i see something wrong i tell him i said 3 10vouches but i leave not knowing its mtn..... outside the store i try loading airtime it doesnt work only to realise its R30 mtn nd it womt work in my cellc phone.... i go back in to the store and explain to him ,his response to me is that he asked me R30 nd i said yes and airtime is non refundable so theres nothing he or i can do i must just take it.... i ask him to call his manager he calls the guy next to him the apparent manager and explains to him that i asked him for R30 mtn airtime and i am lying i did not ask for cellc he insists to his manager he asked me twice and i said yes mtn airtime.....then after all this he refuses to help me saying that cellc airtime is offline.... because of this Consultant i will never purchase anythung at cna again