To let users consent to data exchange is only one side of the coin – they must also be able to withdraw their consents at a later time. This follows from the legal definition of consent but only applies if information about the consents is stored eg. to allow the user not to consent to the same data transfer again and again.
If a user at some point in time should choose to withdraw her (stored) consent to data exchange this must of course be supported by some sort of user (friendly) interface – but note that by deleting information about a given consent to data exchange it does not follow that also the actual data, which was then transferred, must also be deleted.
It is only the stored information about the action of consenting that is deleted.
Weather the receiver of the data about the user, typically a service provider of some kind, is obliged to delete the user info in question, is up to the local legislation to decide.