No Callback after multiple follow ups

I have phoned 5 times now to discuss the credit note that was generated on my account and every single time they say that the person that created the credit note is busy and they will email him to phone me back but still no response. If that person is too busy can I please speak to someone else. All I want is to clarify the amount of the credit note, because if you credit one of the two pro-rata amounts then why is it not credited in full?