sql selecting rows many new date

using following query results, i'm looking many new opening where chargeid chargetype unique.

select chargeid, chargetype, servicemonth invoice

    chargeid    chargetype  servicemonth
1   101     r       8/1/2008
2   161     n       2/1/2008
3   101     r       2/1/2008
4   101     r       3/1/2008
5   101     r       4/1/2008
6   101     r       5/1/2008
7   101     r       6/1/2008
8   101     r       7/1/2008

desired:

    chargeid    chargetype  servicemonth
1   101     r       8/1/2008
2   161     n       2/1/2008