Supersonic bad service

Supersonic is the worst service provider, its a company led by ******. Last month I made a topup, money was deducted but the topped wasn't processed. This month I have been overcharged on both my accounts. The call agents told me that they can give me data amounting to the money that iv been overcharged. I asked for a refund and I was told that it will be processed after 21 days. I then asked the reason why it takes 21 days and I was told that the accounts department needs to investigate. What puzzles me is, why investigate when I choose the option of a refund? And also what investigation has to be made when they can see on their system that they overcharged me.