how to change the incident status from Pending customer to other status

Dear All,

I have a requirement to change the incident status from Pending customer to Reassigned when an end user updates the SD in ess.do page.

Currently, when L1 engineer needs more info, they put the update the tickt and put the IM status to Pending customer, and ess user receives the email to input the SD, ess user updates the SD, as soon as ess user updaes the SD in ess.do page, corresponding related IM to this SD status changing to Work In progress from Pending Customer.

Please let me know how to change this.

Thanks,

JAgan