Taking clients for granted

Cellc they are refusing to refund my money that they debited by mistake, i made payment of R1200 on the 14 April to them, then my account was no longer on arrears then also sent proof of payment. i was surprised see the debit order of R914 go through, then i contacted them to question the error, the consultant noticed the error, then i explained that i want the money to be refunded back to my bank account because its a school fees for my son, the lady told me that they are going to credit the money into my the next months instalment, i did not agree when she says because the money must be used to pay the school fees, and i also indicated that the school penalize me for paying late, then she said they will escalate the issue for a refund, then on friday i got an SMS that i must email proof of payment in order for the them to process the refund and its gona take 7 working days, now today i am told that they cnt refund but the money is already credited to my next months instalment. This is very disrespectful and undermining me and wasting my time, just imagine, i have been counting that 7 days last week, now today those days of last week are not counted and they are refusing to refund me, why did they send me SMS that they want me to send proof of payment in order to process the payment while they were lying to me? This company doesnt respect its clients, i am taken for granted. i want my full amount refund back into my bank account within 24 hours or else they are going to refund R914 plus penalty fee that il be charged for late payment at school.