The reason they are calling you is to make it as easy to use as possible for you. They will want to know what kind of outlet you will be plugging the thing into so when you get it, it literally is plug and play, and you won't have to get an electrician to put in a new plug for you or find some sort of goofy adapter which may or may not work for you. This is info you should make sure they receive, or your dealer so that you can be supplied with the proper plug.
Note, if you are a US customer and go with the Level 2 charger that does 240 volts, you CAN use it to charge on 115 volt too, however the adapters you find online, most of them don't work because they are wired incorrectly, with the power lead, tapped to both hots, instead of one being tied to the N for the 115 return on what would otherwise be a 'power leg'. It's super easy to make an adapter though that literally is a female of XX connector you got for your 240 plug, and a M of the 115 outlet that YOU wired correctly across the hots.
Aaron