How can I change default apex class (to custom class) in inbound settings on social customer service page? In company we have enterprise edition.
If you are using the Starter Pack this is not possible as per the Salesforce help.
If you aren’t using the Starter Pack, you can customize the default Apex class to specify how inbound social content is processed.
Assuming that you are using Radian 6 and Social Studio you can do it as follows Setup>Build>Customise>Social Media>Setup Social Customer Service
Then select the Inbound Settings tab and select the custom class instead of using the default class. This is only possible once the custom class has been created and deployed to the environment.
There will be a list of the classes which includes the references to the Social.InboundSocialPostHandlerImpl like in the standard Apex supplied
global class MyInboundSocialPostHandlerImpl extends Social.InboundSocialPostHandlerImpl implements Social.InboundSocialPostHandler