unacceptable customer service and incorrectly charged

Poor customer service is an understatement, and written confirmation of debit orders being adjusted, and still I am incorrectly debited. on 19/02/2019 I sent through a downgrade form to Trueman Twala in customer services. I received a read receipt, no response from him. I followed up on 25/02 and 14/03, and still no response. I contacted Lisa Wagner who said it would be sorted out. On 25/03 I received confirmation that the debit had been adjusted. On 23/04 I followed up with Lisa and Trueman as to why the debit order had still not been adjusted. It was confirmed once again that it had. on 03/05 the incorrect debit order still went off! That means February, March, April and May I was charged incorrectly. I have successfully downgraded, and want a refund for those four months that I was overcharged.