My advice: use Indecopi (
INDECOPI :: Presenta tu reclamo) the Peruvian customer protection agency. They mediated between LA and me in a clame for a problem with a flight and within 1 week I had the issue solved...
It is in Spanish. Select transporte, click Crear, and fill the form (use Google translate to help with filling the forms, but fill it in English and select in "Elija la oficina del INDECOPI más cercana a su domicilio:", "Indecopi Aeropuerto Zona Internacional" they are the office of the agency that works in the International terminal of Lima's airport and I'm quite sure that if you present your claim in English should be able to help you. Alternatively you can give them a call to these phones (use skype), and try to explain the case and they should be able to provide you support in English:
Tel.: 5112247800, annex 3202
Tel: 5115171845
51 is Peru's international calling prefix and 1 is Lima's.