Battling to cancel contract

I'm trying to cancel my data contract for ***. Phoned *** to start the process. The gentleman tries to sell me a cheaper contract, but I'm not interested. He says he will phone me back in 5 minutes as the system is slow. I'm still waiting to be called back. I just want my contract cancelled asap. I'm not phoning again as it was the third time. I just want confirmation now via sms that my contract has been cancelled.