Try threatening them. Sometimes tough love works.

The only thing I know of that works is waiting. However, it's June, so I'd be seriously considering returning them for a refund.

I missed where you are located. If it is a cold area, and you bought potted trees, sometimes they have leafed out in the nursery and get the baby leaves frozen off when they are moved to the cold area to be sold. They will then look like they are dormant, but they are not. If the branches have a few frilly dry bits clinging to them, that is what happened to your trees.