old mutual money account

I went to their atm to withdraw money then the machine didn't give me the money then i just thought to myself that maybe it didn't have money but to my surprise i received an sms saying i have withdrawn money then i called the number on the atm they advised me to go to the branch tomorrow as it was on sunday fine Monday i went to the branch and they said they have lodged a despite and the money will be in my account within a day or 2 then today i received an sms saying R100 was returned to my account i was surprised cause the money that i wanted to withdraw was 900 so y are they giving me 100 i called them and they told me that they have returned 400 the same day then today they decided to give me 100 back i told them that i have not received that 400 and why did they split the payment cause i requested 500 the first time then 400 the second time then they told me that the 400 they will only lodge a dispute today and maybe i will get it tomorrow how cause the dispute was logged the very same day and again how come you take 500 and return 400 then 100 days after they cant answer that but the 400 is missing and the 100 was deposited and has a reference but that 400 they claimed has been returned does not a have a reference, i just want old mutual to give me back my money and i heard that their atm is always malfunctioning but still they advise us clients to use it then they rob you from it cause now i was ****** and they cant even trace that money but they claim it was paid into my account but there is nothing in my account.