Terrible service

Please help me by instructing vodacom to terminate my data contract, I have sent an email requesting that they terminate my data contract with immediate effect but they refused. I sent the email and called the 3 months back but I haven't received confirmation that they have done it, then I decided to stop the debit order of their refusal. I decided to terminate the contract because the value the data was no longer the same, the data that used to last for a month was only finished in 15 days, I ddnt make sense for me then I decided to cancel. I want vodacom to terminate my contract with immediate effect then il pay for those two months! M fed up about vodacom. Their data is becoming like a ****, I don't want anymore.