there are drugs to dry up milk, but they have side effects.
It can take some months after stopping weaning for milk to completely disappear. How long ago did you stop breastfeeding.
Also don't squeeze them - even to check (well maybe once a month or so). If you stimulate them by squeezing you will also slow down how long it takes to dry up.
I've heard of putting cabbage leaves in your bra to help milk dry up...
As supersally said, as long as you are not stimulating them they should dry up naturally. This can take any matter of months. Especially considering the child is still an infant and her cries ect are most likely triggering your letdown. The body intends to breastfeed for as long as possible, so it may be a while longer before it gives up.