Supersonic does not answer phones, whatsapp line doesn't work, terrible customer service

Supersonic does not get back to their clients after a call was logged. They debited my account with the wrong amount after i downgraded my plan and when i sent the debit order back and asked them to reload the debit order with the correct amount they told me they don't reload debit orders so now i have to pay cash every month, even though it was their fault. They don't answer their phones before it rang at least for 10 minutes or longer and they don't answer on their WhatsApp line either. They don't even respond when you load a ticket and tell them they are definitely the worst service provider around.