You have no need to tell them that!
Turn on your VPN in a country which is privacy sensitive and inform them that you are withdrawing consent to storing or processing your data.
I've dropped a template below which sums up some GDPR directives.
Tap for spoiler
To Whom It May Concern:
I am hereby requesting immediate erasure of personal data concerning me according to Article 17 GDPR.
Please erase all personal data concerning me as defined by Article 4(1) GDPR.
-name and surname -email address -phone number -home address -date of birth -race -gender -political opinions -credit card numbers -health data -images that include biometric data (face, retina, fingerprint) -identification number -cookie ID -internet protocol (IP) address -location data -advertising identifier of my devices -logs of my activity -typing habits -voice recordings/samples -height/weight data -residential status -profession/hobbies -skills/talents
I am of the opinion that the requirements set forth in Article 17(1) GDPR are fulfilled. You cannot claim an exception based on Article 17(3) GDPR either, particularly as I am not a public figure.
If I have given consent to the processing of my personal data (e.g. according to Article 6(1) or Article 9(2) GDPR), I am hereby withdrawing said consent for the entire process. In addition, I am objecting to the processing of personal data concerning me (which includes profiling), according to Article 21 GDPR. I request that you restrict the processing of the data concerning me pending the verification whether your legitimate grounds override mine, pursuant to Art. 18(1)(d) GDPR.
If you have made the aforementioned data public, you are obliged pursuant to Article 17(2) GDPR to take all reasonable steps to inform other controllers, including search engine operators, who process the personal data listed above, that I have requested the erasure of all links, copies or replications. This applies not only to exact copies of the data concerned, but also to those from which information contained in the data concerned can be derived.
In case you have disclosed the affected personal data to third parties, you have to communicate my request for erasure of the affected personal data, as well as any references to it, to each recipient as laid down in Article 19 GDPR. Please also inform me about those recipients.
If you object to the requested erasure, you have to justify that to me.
My request explicitly includes any other services and companies for which you are the controller as defined by Article 4(7) GDPR.
As laid down in Article 12(3) GDPR, you have to confirm the erasure to me without undue delay and in any event within one month of receipt of the request.
I am including the following information necessary for the sole purpose of identifying my data:
If you do not answer my request within the stated period, I am reserving the right to take legal action against you and to lodge a complaint with the responsible supervisory authority.
Thank you in advance.
Yours sincerely, (Your name here)