Returning a Kindle

I was given a lovely wifi Kindle for my birthday, but being an awkward type, I decided that I would really like to have the 3G version, just for those odd occasions when it would be nice to have internet on it when out  and about without fiddling about looking for wifi hotspots and changing settings.
( in which I witter on about returning a Kindle in more detail than any normal person would wish to impart, probably of interest only to someone else who feels the need to return a Kindle )