Dissapointed Vodacom Customer

I've been a Vodacom customer for more than 15 years. I upgraded my phone at the end of August last year (2025). However Vodacom doubled billed me for the old handset for 3 months. I did phone customer service in September and was told they will fix the error, but with no result. I am still trying to get reimbursed with no success. Vodacom makes it impossible to lodge complaints and receive responses. I requested many times to speak to a supervisor or manager and was told they are busy and they will phone me back. Again this never materialized.