Create customers with phone number only!

We use zammad for email and phone support. What we would like to be able to do is:

api call that creates a ticket for a new or existing customer identified by phone only!
Reason is: we get phone calls and callback requests and want to manage them in zammad. Often you dont’t understand the customers real name. So the only reliable information we have is the phone number. At this stage we dont’t have a email from the customer.

It would also be nice to join two customers. I.e you get a call and a separate email from the same customer. Or the customer uses two different email addresses and you want to keep an overview.