Spanish to English Medical Medical (general) Finance

Hello fellow linguists:

I have a terminology question from the world of Puerto Rican medical finance. This comes from a patient's bill listing Patient Name, bill number, form of payment and, at the very end:

Recaudador: [ ] Oficial, [ ] Auxiliar, [ ] Sustituto

I found "oficial" as "financial collection officer" in the proz glossaries, but I am unsure about these three terms in general. Any suggestions are highly appreciated.

TIA!

JM