I created a simple model x_ovh_phone to follow phone calls (data are pushed by our OVH call center).

Fields are x_date, x_description, x_call_duration and a many2one field to connect to helpdesk.ticket

In helpdesk formview, I used Studio to add a one2many field associated to the many2one of x_ovh_phone

  <xpath expr="/form[1]/sheet[1]/group[1]" position="after">

      <field name="x_studio_field_9WAxj" mode="tree">

        <tree string="Liste des appels">

          <field name="x_date"/>

          <field name="x_call_direction"/>

          <field name="x_studio_field_9Db5i"/>

          <field name="x_call_duration_display"/>

        </tree>

      </field>

    </xpath>

  </xpath>