I receive spam messages on Msn from T-Mobile users. How can I report/avoid those ?

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Here is a copy of some messages I received. It is coming from contacts that are not registered/allowed on my Msn account.

[email protected]: I saw ur pics on ur online profile, You look Cute . Lets hookup xoxo . msg me here - http://www.singleadultmeetup.com

Sent From T-Mobile Mobile ID: 74401

__________ __________

[email protected]: Hey my friend wanted me 2 show u this http://www.singleadultmeetup.com

Sent From iPhone Mobile ID: 99810

_________ _________

[email protected]: Hot Local Singles http://www.singleadultmeetup.com

Sent From AT&T Mobile ID: 80860

_________ _________

[email protected]: Cute Local Singles www.singleadultmeetup.com

Sent From Sprint Mobile ID: 21446
Note that I receive these messages as "instant messaging", not email.