MTN Upgrade - Poor Service & Stock Problem

Good day,

Can anybody give me an email address for MTN Direct Complaints department, reason, if I call MTN Direct ***, regarding an Upgrade, always being transferred to the Agent who assisted me with the Upgrade and then that person is not available, and if I asked if another agent can assist, the answer I get "Sorry the Agent who assisted you, that person is assigned to your Upgrade"

Kind Regards