This. I would also suggest so that it is on record, notifying NVC of the withdrawal as well. As per Mike’s post above it can (and must here) be done, but it must be done in writing.
The safest course of action is probably to communicate with both the NVC and the appropriate U.S. consulate. The request to withdraw a Form I-864 must be made in writing. When communicating the NVC you must include the visa application case number, as assigned by the NVC. This number can be found on the invoices issued by the NVC. (There will be one for the DS-260 and another for the Form I-864 – the invoice IDs will be different, but case number the same). The withdrawal letter should list the applicant’s full name and date of birth, along with the NVC case number.
The withdrawal letter should also be sent to the appropriate U.S. consulate. This can be somewhat trickier. Each consulate has an “immigrant visa” unit that processes permanent (i.e., “immigrant”) visa applications. But each consulate has different practices for how the immigrant visa unit communicates with applicants.
The written request to withdraw the Form I-864 should be sent in hard copy to the appropriate consulate – contact information can be found here. The letter should contain all the information included in the NVC letter. The letter should be sent with delivery confirmation. For guidelines on submitting immigrant visa-related documents to consulates, see the drop-down list on this Department of State page.
https://www.soundimmigration.com/withdraw-form-864-affidavit-support/