As I've asked previously, how much weight can you really put on this testimony? Trying to report a crime is not the same as reporting a crime. We have no evidence of a call made to the wrong security company, this is only witness testimony. OK, they realise it's the wrong security company, the logical next step is...you phone the correct security company. Ah, problem here, the couple don't have the number of the security company where they live. Why? Were they abroad or at work or somewhere they would not be expected to have the number? No, they were in their house, the most reasonable place you would be expected to have the number.
I put it to you, that if Reeva died as a result of OP claiming that he phoned an ambulance that didn't turn up, how much weight would you give to his testimony if his reply was, 'well I did phone an ambulance, but I phoned one from where I used to live by mistake'. Ah, but presumably you immediately then phoned the correct one? 'Well er no, I just left it'.
I'm not convinced that Ms Burger didn't hear anything that night. But I'm also far from convinced beyond reasonable doubt that she did.