You might try e-mailing email@example.com, but you may not get an answer. Might be better to just call BTL at 2-77690.
Last I heard, BTL charged a BZE$35 activation fee, plus $4 a day if you used your own phone or BZE$9 if you used theirs, plus about 85 BZE cents a minute within Belize. I had not heard of the "international roaming charges" if using your own cell phone. I thought the only long-distance charge was what BTL charges, which is outrageous enough.
Please let us know what you find out.