Hi Travis,
Thanks for your reply. I am able to get all the leads activities through getLeadChanges soap method. 
This method returns below activity attributes in response:
- 
		Mailing ID
- 
		Step ID 
- 
		Choice Number 
- 
		Category 
- 
		Subcategory 
	All these attributes are  some kins of IDs. Can you please provide the details what these attributes are. How can I get the detailed information of these attributes.
	thanks!