withdrawing consent related to delivery (email&phone nr) in Germany

I've seen some strange information that 1) German customers have to explicitly consent to have their email and telephone number to passed to the delivery company Art. 6 Abs. 1 S. 1 lit. a DSGVO (I am talking about an online store and fulfillment of customers orders so is often required by for example courier companies) 2) and that they can withdraw that consent during or after they place their order. And that they can (or should be allowed and that info should be in the privacy policy) to withdraw that consent either by contacting us (the online shop) or the shipping company themselves. well that sounds not only problematic but most of all undoable .... Can you verify?