Double debited

I was double debited on the 5th August and again on the 31st August. The agreement was for the 1st of the month. Call center agents are *********** Everytime I speak with them. And when my issue cannot be resolved they suddenly cannot hear me and end the call. They confirm all my details yet they don't bother calling me back. I want to be reimbursed for the 1 debit that went through including my airtime I've wasted speaking to the agents.