Old Mutual bad service

I emailed Old Mutual in August about a retirement annuity. I received no reply. I then phoned and was told to send my query elsewhere. I emailed on 8 September and received no response. I emailed again yesterday and I don't expect a response.

I phoned the call centre yesterday and held on for half an hour, but no one answered. I tried again today but there was no reply.

All I want to do is cancel the monthly payments for my retirement annuity. The payments go through via a debit order I am not able to stop from my side. The payment for September went through and the payment for October will most likely also go through.