Custom field with the value "user.phone" from the integration with CTI

Hello, we have article where where integration with PBX is described:

https://docs.microfocus.com/itom/SMAX:2020.05/ctiLiveSupport

And we have example:

https://sma.itSMAX.io/saw/cti?TENANTID=xxxxx&field1Name=user.phone&field1Value=792-3599999

For a service request I need to add a custom field where the caller's phone number will be stored, obtained from this string from the value "user.phone".

Can I somehow intercept the value of this field and add on the form Live Support?