Change Domain Owner / Whois for my customer

I have the WHOIS data for a domain, such as .com (owner, tech, admin, etc.). How can I change this data for my customer? I buy domains on behalf of my customers and manage them. But of course, my customer should be listed there, not me. But I can't see anywhere in the OVH panel how to enter a different owner, admin, tech, etc. contact than my own account, which is obviously incredibly stupid.