Incorrect Billing

I upgraded my phone & the new contract kicked in on 14/12/2015.I added a data pack of 1GB which was an additional charge of R57.I requested a R50 limit on excess usage in case I depleted the amount given on the plan.Everything seemed fine,however I noticed that my airtime was depleting fast.I decided not to make any calls but the excess charges continued.I went online and noticed that using the internet is charging me instead of using my data.I called Cell C only to be advised its a store error and they should fix it.I went to the store & explained the issue,I was advised that a BB package was added which isn't compatible with LG.The rep corrected her mistake and added 200MB.I told her i refuse to pay the excess & she advised she will get back to me.This never happened & the full amount was deducted from my bank acc.I went back to the store & was offered R57 to cover the data pack.I refused the offer & was told this will be escalated. 1 Follow-up was done and nothing after that. I continuously have to chase up on this issue which is poor customer service.I would like the R152 excess charges to be refunded back to my bank account.