Capitec took my money and will not asssit me!!

In July i withdrew my old age grant from a capitec teller in a supermarket, i withdrew 1600 and the atm only gave me 1000 and when i did a balance it showed 200 left in the account so R400 was taken by the atm. I went to the bank on the 5th of july and they said they will investigate, its now the 22 of july and still capitec cannot help me now they say its head office problem. I am in my 60's, a pensioner and R400 is a lot for me. I am so dissapointed in capitec, just goes to show they dont want to help me and keep saying its someone elses problem! I want to close my acc and move to another bank...