I have been a member of this forum for over 14 years, and it is amazing to me that this voltage question is still be discussed, and presented incorrectly by so many members with the end result that new members become confused and continue the misconception.

Please look at this image. Study it. Save it for future reference. This is what a 50 amp RV service looks like, including, yes, believe it or not, including 240 volts. It is there. You can measure it with a voltmeter. Is there a lot more to it? Yes, but it exists.