where did my money go??

I currently have a contract with VODACOM for my smart phone,i have actually been a customer for a while.I recently updated my account payment date from the 1st to the 15 of every month because my salary date changed. Vodacom used to debit my account whenever so i cancelled the debit order option and decided to go into the store on a monthly bases and make payment and did my best to ensure the account is always up to date.On the 15th February Vodacom debited 2400+ from my account without any authorization from me,I contacted the call centre and they kept transferring me from one department to the next,i Ended up speaking to a lady by the name Nomfundo who not only did not assist with my query but her tone was patronizing as well,If Vodacom took my money and they cannot tell me why and if the contract is cancelled or what ever the case may be.I will never recommend them to anyone and do not think i will continue with any contract or purchases from them