I think you must still be off frequency. All the MWARA frequencies are whole numbers.
CAR-A
2887.0 5550.0 6577.0 6649.0 8918.0 11396.0 13297.0 17907.0
Barranquilla, Boyeros, Guatemala City, Merida, New York, Panama, Piarco,
San Andres Is., San Jose, Tegucigalpa
CAR-B
3455.0 5520.0 6586.0 8846.0 11330.0 17907.0
Barranquilla, Boyeros, Cayenne, Georgetown, Maiquetia, New York, Panama,
Paramaribo, Piarco, San Andres
The tones that the ground station transmits is called "Selcal" - the pilots don't want to listen to all the other aircraft and background noise so they turn the audio off on their selector panel. Every aircraft with HF radio is given a code that corresponds to 4 musical notes - when the notes are transmitted only the one aircraft with that code will have a chime go off in the cockpit and a light will flash. The pilot will then go on the radio and say "United 1234 answering Selcal" and the ground station will reply.