Can I call the same activity name in call method?

Yes. We can call the same activity name inside the activity itself. This is called Recursion.

• Activity would be saved successfully. No compile time exceptions are thrown during save of the rule. 
• While coding, since this is recursive code: we need to be cautious that it wont enter into infinite loop.
• There will be rare scenarios (requirement) to get into this approach. So double check before entering into this approach. Our break conditions should be accurate while dealing with this. 

Example : ShowCustomerDetails is the activity. Inside this activity, I can call ShowCustomerDetails in its own step.