cell c can't help me cancel the contract

The guy by the name of David Brasco offered me a phone contract, saying its Samsung galaxy 6 & I accepted the offer but to my surprise on the day of delivery it was Ag chrome & I didn't like it so I returned it within 3 days of arrival, I called their call centre & cancelled the contract, here is the reference I was given OPF148051. What is bothering me is that they still debiting my account, I am very angry because since the last 3 months I've been trying to call them about this query but they'd transfer my call then let me hold the whole day without any help