Bad bad experience, horrible customer service!!!!!

I bought some goods and airtime at Grand Parade store in Cape Town on 22 January. Teller was Ryan Evans. When I got home I saw he gave me the wrong network. The airtime was worth R200. I phoned and was assisted by Nikita who assured me she would investigate and try to get my airtime refunded or changed to the correct network. She called back a while later stating that the teller said he asked me if it was the correct network, a lie and that she tried to get branch manager to refund me which they refused. I shop at that branch all the time and I love Ackermans. I am so disappointed at this experience and I am actually thinking of closing my account. I don't need to do business with a company that does not value client service. Only positive is the professional way Nikita handled this query.