Telkom unprofessional

My telkom debit is R388 a month. They debited me for R388 on 30 June 2020. Then sent me a bill for R978. They debited me for R978 on 24 July 2020. That's 3 times my debit amount. I spent 20 minutes trying getting hold of them. When they finally answer and I say hello their network goes blank. How can they debit me 3 times my installment and my account still be blocked. They are ******* and also unprofessional.