To call a customer from an Opportunity Form means you have to open the associated Contact and make the call from there. This also means that the phonecall record created in CRM is associated with the Contact in general, rather than the specific Opportunity.
Follow this procedure to add Phone Number fields to your Opportunity form.
In summary, the process is to add a calculated, custom field (of format “Phone”) to the Opportunity form.
- Go to Settings > Customizations > Customize the system
- Go to Entities > Opportunity > Fields and click NEW
- Set the field properties per this snap
- Click EDIT to set the calculated field properties per this snap
- Close and save everything and Publish All Customizations
Now you just have to add the above created field to your Opportunity Form. It will be a clickable phone number that you can use with Dynamics Telephony click-to-dial, or Skype/Lync click-to-dial
Publish all customizations again.