I am afraid you cannot do that in single request as creating a contact is one scenario and updating a contact is another scenario that's why Hubspot have made two different endpoint.However if you want do both functionalities then you can create a single function in which you can create a contact and then simulatneously update the same contact .I hope this will help.
Hope this helps!
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I use API to get PhoneNumber and dial use pbx and mark as contacted after I sucessfully got. if there is more than one agent use this query the API I'm affraid there will possible duplicate contact received by different agent because updating contact need some time to process.