If it were agreed in advance that you would be getting dual, and logged it as such then I think it could be dual received, assuming the other guy was qualified to teach in the airplane and your status as under-instruction would not conflict with other regs...ie would a 135 OPSPEC allow that under the conditions?
Otherwise...you talking on the radio would help make the case that you were exercising the privileges of your pilot cert. I don't think there's any absolute regulatory requirement that you need a pilot cert to talk on the radio, or that talking on the radio makes you crew but it would certainly tip the scales in favor of crew status IMO.
Talk to a lawyer.