Port change other than 9980

Hello to all,
I’ve a working CODE (no docker) on debian 10 + Apache as RP and wondering if (and how) is it possibile to change default port from 9980 to another.
I saw that in /lib/systemd/system/loolwsd.service i can put an extra option like --o:clientport=xxxx but when i start again loolwsd service it takes again the default port. Is there a way to do that?

Thank you in advance for your support and help!