Zero Customer service when cancelling contract

I have e-mailed ********** three times to give notice that I will not be renewing my data ****le contract which runs out on 15 December 2017. I have phoned their call centre countless times without any joy, I gave up after holding for 10 minutes.

They don't answer their phones, they don't acknowledge receipt of their e-mails. Had exactly the same experience when I cancelled my phone contract. Had hoped that this time around it might be easier. But no such luck.