Should the title be changed when converting a conference article into a journal article?
According to the conference website: 


  The conference proceedings are to be published in the Springer's LNAI (indexed by DBLP, EI, Scopus, and Thomson ISI).


In other words, your conference paper is already published. The journal paper will therefore be a new publication, and as such, you could use a different title, to avoid any confusion (and it will be a different paper, since you have to expand it). 

EDIT
However, there are precedents, for at least one previous edition of the conference you're mentioning, of authors having the same title in the conference and in a journal edition (taken from DBLP): 


Peerasak Intarapaiboon, Ekawit Nantajeewarawat, Thanaruk Theeramunkong: Extracting Chemical Reactions from Thai Text for Semantics-Based Information Retrieval. IEICE Transactions 94-D(3): 479-486 (2011)
Peerasak Intarapaiboon, Ekawit Nantajeewarawat, Thanaruk Theeramunkong: Extracting Chemical Reactions from Thai Text for Semantics-Based Information Retrieval. ACIIDS (1) 2010: 271-281
Yongli Wang, Dongxiao Niu, Ling Ji: Power load forecasting using data mining and knowledge discovery technology. IJIIDS 5(5): 452-467 (2011)
Yongli Wang, Dongxiao Niu, Yakun Wang: Power Load Forecasting Using Data Mining and Knowledge Discovery Technology. ACIIDS (1) 2010: 319-328
Moamin Ahmed, Mohd Sharifuddin Ahmad, Mohd Zaliman M. Yusoff: A Collaborative Framework for Multiagent Systems. IJATS 3(4): 1-18 (2011)
Moamin Ahmed, Mohd Sharifuddin Ahmad, Mohd Zaliman M. Yusoff: A Collaborative Framework for Multiagent Systems. ACIIDS (1) 2010: 329-338


Looking at random references from the journals in question, it seems quite frequent to have the same name for a journal paper and a conference publication the previous year. In other words, I stand corrected, and you might want to keep the same name for the journal version. 

As pointed out by DavidRicherby and Mangara, it's likely to be field dependent. Hence, the best approach is probably to look at previous editions of the journals in question, and check if there are matching conference papers.