PT told me not to do hyperextensions. Should I listen?

So I joined a new gym recently, and the personal trainer that was assigned to me reviewed my workout routine, which is ice cream fitness, and he told me that hyper extensions could injure my back and that instead I should do this sort of exercise where I put my feet up on a medicine ball facing up and curl my ankles towards my butt. Should I listen to him or just do the hyperextensions?