Federal Documents require that the written consent form is documented. The question occurs, how would you get that document when your research is done via phone?
Here are some options:
You may plan to send solicitation materials via email or USPS. Attach a printed consent form and request your volunteers to sign it and send it back (a stamped and addressed return envelope would be nice). The phone call will be conducted after you receive the consent form back (not earlier!)
You may send an email and request a response if the volunteers would like to participate in your study. The returning email is the consent document and should be kept along with all the research documentation.
You may call your volunteers and record the beginning of the conversation when you ask for your participants' consent. Then, if they agree, you may continue the recording, or continue without recording. Please find the sample script below (Script 1 - Recording the Participant's Consent on a Phone)
You may create a record of your opening conversation with the volunteer on paper. Make sure that the volunteer understands the research procedure and answer any questions they may have (make sure that you have a record of those questions and your responses). Please find the sample script below (Script 2 - Recording the Participant's Consent on Paper During the Phone Call)
The options listed above are just examples. Other solutions may be accepted; please describe your plan and we can work on it. As stated on the Informed Consent page, the consent form must include all its elements, must be documented, and obtained before the research procedure begins.