Cell C won't phone back

Can someone at Cell C please phone me! No one at Cell C, including the technical department, can tell me why I was billed R638 on my R69 contract. This supposedly happened in a 40 minute period but my PC does no updates. Each time I phone them they promise me that they'll get someone to phone me within 2 days to explain and each time I just get an sms to my data sim card saying that the data was valid and no phone call. I'm tired of phoning Cell C every week explaining the same problem. Can someone who knows what they're talking about please phone me. The latest reference number is ***. Please phone the number provided. 084...