Hello Jean,

Jamaica has two GSM networks:

Cable & Wireless Jamaica - GSM 1900
Mossel - GSM 900

According to the Motorola (USA) website, the T720 is a dual-band 850/1900
phone.  According to gsmworld.com, C&W Jamaica does not have any roaming
agreements/partnerships with any other providers.  (Conversely, a check
of Rogers shows they don't have any agreements, either).

You would definately need to get your phone unlocked.  This may cost you
a little bit.  I would recommend that you first call Rogers and ask if they
have roaming in Jamaica.  When they say no, ask if they'll unlock your
phone for you, because you will then need go with a prepaid/PAYG setup
with C&W Jamaica (Visit: http://www.cwmobile.com/jamaica/bFree_index.asp
for info).  

Hope this helps,
rev