By email, of course.
You really have to question people's grasp of customer service when it allows for email to be Telephone Systems Customer Support's only means of contact.
Clear time stamped audit trail.
Though honestly, I prefer web chat for dealing with tech support. I like being able to not have a handset pressed against my head for three hours while I follow a script following Indian dude who ignores the actual diagnosis that I provided within the first thirty seconds of the conversation. Such as we've lost two hard drives and are one drive away from having to rebuild a LUN. I absolutely hate and abhor trying to CALL anyone for customer service. There's a handful of companies that don't suck (USAA), but the overwhelming majority go straight to a script reading Indian dude who cannot deviate from the script. You'd think they were holding guns on his family.
People learn to read and write much quicker than speaking. If I'm forced to deal with crap tech support, I at least need to understand what they're saying and that rarely happens with phone calls.