Yes they do. So your first bill would have about 40 days of monthly charges opposed to the usual 30 days.
When you look at the first bill, look at the page that has the head of "Account Detail." That section will have your monthly rate plan with twio sets of dates in ().
Your monthly services for the approx 10 days plus the one month in advance.
Keep in mind, the mminutes with your plan will be prorated as well so for the 10 days, you would not have the full amount of minutes that your plan would usually have.