Vodacom *******ly billed me for there "discount" on a contract that ended on month 24!

Vodacom charge me there "discount" on a contract that already expired after the 24 month period. My one data contract was cancelled a month before the expiry end date. I have spent 25 minutes with call ref nr *** to end the contract in time. Then they still ignore this and charge me for data on month 25 that I never received. I e-mailed the customercare e-mail and eventually they cancel the wrongly charged amount with a credit note. Then this month I received a invoice for THERE DISCOUNT for the month 25 that I did not have a contract. E-mailed them again, but this time around I do not even get a reference number. Please refund me your own discount that you charged to my debit order!!!!!!