I posted the following in the forum.. https://www.zabbix.com/forum/zabbix-help/367999-event-unackowledge-or-add-event-message-and-unacknowledge

In Zabbix 3.2, looking to use API to update an event with an ITSM incident # that we auto generated. Problem being when i update the message field in the event acknowledge it always completes the acknowledgement. Is there a way to place data in the event with the ITSM ticket # without the acknowledge? Or perhaps go back after placing the ticket # in and force the unacknowledge? We need the help desk to do the acknowledgement of the event. 

Currently:
my $ackEvents = $apiSession -> do ( 'event.acknowledge', { eventids => "$eventId", message => "$incNumber", action => 0 } );

So,even with Action =>0 it acknowledges. 

Any other ways to provide the ticket # from ITSM without the disrupting the acknowledgment?

Or is there a way to update an event tag via API so we can place the incident # in the tag and not have to worry about the ACK?