I would be interest in a phone call debate. It is much easier for me to speak than to type. I would also like to hear/see other peoples arguments that are opposed to mine. Not to say that they are wrong but to get insight on why people have a different view on my beliefs.
Yes, people would be interested in having a phone call debate, because it would give people a chance to participate in a debate that might not be able to participate in any other way. Also, a cell phone debate would give people a chance to view the candidates in a different light, without considering what they look like when they are speaking. Listeners could focus on the message, more than appearances.