standadr bank put me in debts

i made a purchase in pnp in April,and money was take off my account.to my surprise in October WHEN I CHECKED MY BALANCE I WAS LEFT WITH MINUS -1633.i went to the branch in the glen to complain cause i thought it could be that the is someone doing ***** on my account. the closed my card and headed my query to the ***** dept. i then received a call frm thr ***** telling me that i was a purchase made in in April that did not go off . i then asked the agent then what happen to my money then at the time cos if i have 7000 and i make use of 1000 am left with 6000 and wht ever i us it will be for that amount.he sent me to my branch i tell him i dont have a branch i took this account on the phone.and he said he doesn't knw went to the branch in the glen even in the one in cresta where i fetch my card at they cant explain wht happen,right knw am sitting on a bill of .3000 and couple that i cant even affourd to play and i have been served aswell by standard bank for some thing i dont knw and this money is increasing evrytime and i dont get help.please assist