In reply to Danil:
Hi Danil,
unfortunately I do not see all your code and I do not understand why you want to modify the variable i_rsp_credit in the virtual sequence.
It is good practice to pass variables/paramters through the testbench hierarchy. This allows you to retrieve the actual value of a variable in any component of your testbench. Typically it should be set in a corresponding test.
By the way there is no reason to register a configuration object with the factory. This gives you more freedom to implement the configuration class.
Hope this helps.