Working on something I wasn't hired for

So,
I'm a general cleaner, and have been doing so for the past 7 months, even got my permanent contract. Now, due to the lost of contract between my employer and one of the places I work, my company is changing my shift and the places where I work. So far, everything is understandable and OK.

But here's the catch.

One of the new places I'm being assigned to, the job expected for me to do is of a Warehouse Operative and not a Cleaner. And I do not want to do that, since it's not what I applied for, also because the odds of me hurting my back are much bigger.

I wonder I can do that won't lead me to losing my job.

Thank you,