Change labels at SSRSReport contract class

hey all,

** Microsoft Dynamics AX 2012 R2**

i want to change two labels at: cash and bank management > reports > transactions > bank statement 

there's to labels, 1- Opening 2-Closing ,, i want to change them to 1- Date from 2- Date to ...

i opened the report contract class : BankAccountStatementContract , and changed them, and closed the AX, restarted the service,, but it doesn't work

please if anyone can help,

thanks