help required pls

[daunorubicin]

I am a doctor and I applied for an elective rotaion in a US hospital.I applied for visa and they gave me 6 month b1/b2 visa with annotation that i m going to US for elective rotation in that specific hospital.Due to family problem I was not being able to go there.I requested them to postpone my rotation by few days.They cancelled it.
Now I am in a big problem.I dont go there as my rotation in that hospital is cancelled.I have to go there in april for one of my medical licensure exam.I contacted embassy and they said that I can only travel to US as long as my purpose of going there remains same.
WHAT should I do.should i get this visa cancelled.i have heard that not availing visa counts v negatively for any future visa.

[PraetorianXI]

You will have to re-apply for a visa again. It will be CWOP (cancelled without prejudice) which won't affect you.

[daunorubicin]

thanx Pretorian.
Do i have to apply for cancellation.how should i proceed from here.
thanx a lot

[PraetorianXI]

Just apply for a new visa. The VO will cancel it at the interview for the new visa.