Privacy policy often states that one can "withdraw consent" to the collection, use and disclosure of personal data. Unfortunately, it is often the case that consent was given to the collection, use and disclosure of personal data for a particular use case, but somehow the data was used for other unstated use cases.
How can I "withdraw consent" without implying consent was ever given, so that I reserve the right to take further action in the future?
You could say something like "I do not consent to [XYZ], and I revoke any consent I may have given in the past." That makes it clear that you intend to revoke consent, without acknowledging that you ever did consent.
If you have previously given consent, the most honest and correct response is “I withdraw consent.”
If you state “I have not given consent” that could be proven false, and undermine your credibility.
A neutral response would be “I do not give consent”. This says nothing about past actions, (or inaction in the case of opting out) but clearly indicates your intentions going forward.
My consent for the collection and use of my personal data (previously only given for the purpose of doing $x) is hereby withdrawn for every and all purposes.