Data validation, incorrect billing

I have a R149 pm (2G) data contract with Cell C since 2011. Every month my account is debited with R149 with one or two exceptions, reaching not more than a R500 bill.<br> <br> In December of 2014 I received a bill of R2281.27 - I was away on holiday.<br> In January of 2015 I received a bill of R5051.82. <br> <br> On 2/2/2015 I went to my nearest branch (Brooklyn) to enquire. I requested an inquiry, since I used my tablet in the same manner as before.<br> <br> On 11/2/2015 the response was: \A data validation was done and we picked up that data usage is not valid. We have now logged a case to Billing for a refund."<br> <br> I was very satisfied since I was promised a full refund by the branch manager.<br> <br> I waited for the end of the month - no payment!<br> <br> I enquired again - only to be told that they will pay me R71"