SBVAF can't seem to keep a promise to call back

On 14 March 2016 I called the call centre to enquire about paying in extra money into my vehicle loan in order to save some interest. I was informed to transfer the funds to a bank account and then call back after 3 days, which I did. I then requested the funds to be taken off the outstanding capital and then reduce the payback period. A request was loaded, which according to the call centre representative will be processed by the 5th of April 2016. I was a bit negative since I would then be losing out on half a month's interest but I left it there. The 5th came and went, I called the centre again on the 6th and was told that the person working on the request will call me back urgently. I phoned again today the 7th, and was told the same thing, I then demanded to speak to the team leader, I was told to hold, after 15 minutes with no response I hung up the phone and called again, speaking to another consultant and requested again to speak to the team leader, I was asked to hold again. After 5 minutes the consultant told me the team leader would look into the request and call me back, this has not happened. I don't know how to further elevate this... I'm losing money!!