Hi Abir,

When you call an onchange function you can access any value from that model through self. For example:

@api.onchange('mobile')
def onchange_phone(self):
    # for example: get the value from the field 'mobile' in a variable named 'mobile'
    mobile = self.mobile
    # Set a static value on the field 'phone'. You can also use the 'mobile' variable or anything else here.
    self.phone = '014'

Regards,
Yenthe