How to change levels?

Hello!
I have got a dataframe with 10 columns and 100 rows. The seventh column 
consists of a lot of country names.
When I use newdata=subset(data, data[, 7]=="United Kingdom"|data[, 
7]=="Germany") I get just the rows where the country name is UK or 
Germany.
But the level information doesn`t change. That means if I use 
levels(newdata[,7]), I get:

  [1] "Austria"                  "Belgium"
  [3] "Denmark"                  "Finland"
  [5] "France"                   "Germany"
  [7] "Spain"                    "Sweden"
  [9] "Switzerland"              "The Netherlands"
  [11] "United Kingdom"           "United States of America"
That leads to problems in the further data processing .

How can I change the level information to the real levels of newdata?

Thanking you in anticipation

Claudia