Not able to downgrade service

Phoned 10210 and pressed option for downgrades - consultant directed me to 10213.

Phoned 10213 and pressed option for downgrade and consultant said I should e-mail servcancellation, which I did and received back a form that is only for cancellations and not for downgrades.

All I want to do is downgrade my fibre from 10MBPS line to a 4MBPS line.

Also, my December account has a "General adjustment"for R385, which I have complained and not yet received a credit. I am unsure as to what this charge is for,