in principle you should be able to reject the mortgage sale, too. purely hypothetical but: suppose some bank was responsible for killing a family member, you shouldn't be forced to owe that bank money.

This means that any mortgage transfer would come with a 'sweetener deal'. If you don't object to the transfer you get a small reduction in your monthlies, e.g.

I assume the right to sell the mortgage to anyone they want is part of the original mortgage contract.