Telkom Billing Complaint

Today I called Telkom mobile 3 times spoke to Hazel, Collen Mlambo & Lastly Philile, the all couldn't solve my billing issue, I took out a 2 year data contract for R129p/m it all went well till the Jan 2018 when I was billed R234.38 instead of the normal R129 I usually pay then Feb to April I was debited R228 monthly and now in May got billed R458.33 I checked my statement from last year till now and realised I've been over charged and now when I want to be reimbursed they say cause I used the data they can’t reimburse me however I did not change my contract and have never called them to do so. Collen Mlambo and Philile also dropped a call on me after spending over 2 hours this morning to try and resolve this issue. May I please be reimbursed R458.33 which is the amount I’ve been over charged by from Jan to May and keep my contract on R129 till it ends.