... Deny service if the customer no longer grants you access to personal data not essential for you to provide the service. A delivery address is essential in o

... Deny service if the customer no longer grants you access to personal data not essential for you to provide the service. A delivery address is essential in order to be able to deliver goods, shoe size is essential in order to deliver shoes - shoe size and address isn't essential in order to allow pseudonymous messaging. You are in general, not allowed to store personal data without "proper purpose" even with content - the GDPR has provisions against data mining.