Refusal to Cancel a month-to-month sim only contra

I took a 2,5gig month-to-month sim only data contract,having been informed I could cancel giving 1 month notice. Completed and submitted prescribed cancellation for on 03 December 2015 and told I would serve 21 days notice.I further sent the same forms over 10 times to different individuals who promised to \escalate\" to supervisor and sometimes to team leader. Number owner tried to port severally but was told it's still on contract. Telkom continued to load data to cell number. Monday 14 March 2016 they texted me saying they will reverse the charges and process cancellation. Tuesday 15 March 2016 they said they are still investigating. "