Account problems that they fail to sort out

Have been a Cell C customer for 15 years. They double debit my account on 1 August, then on 1 September they did the same. I have been trying for 10 days to get my money back, have been into the CelC shops twice, promises are made and nothing happens. When i phone they tell me it will be sorted out in 48 hour, or someone will call me back today, it never happens. I am sooo disapointed in Cell C, was always a loyal cuatomer.