if only one LCI is activated, does that still voids the warranty??
In general, activation of any liquid indicator can be grounds for voiding the warranty.
How can I proove that the phone hasnt had any water/liquids issue?
You probably can't. I can't think of any way you can prove that no liquid ever got into the iPhone, there being evidence to the contrary.
The city I live in is 99% humid and I live a few blocks from the ocean. Can the enviroment activate the LCI??
Unlikely, but I can't say it's impossible.
Sorry, but since Movistar is the support provider for iPhones sold by them in Peru, if they say that the warranty has been voided, there's probably nothing you can do other than pay the replacement charge. You can try asking to speak with a manager and pleading your case, but again, all they can go by is the evidence they see, and if they see a liquid infiltration indicator triggered, that's probably what they'll believe.
Thanks for your reply.
So basically there isnt anything I could do?
If I take it to an Apple Store in the US, would they do something? I think they'll be "nicer" than Movistar.
I read on the support page that they can look for signs of corrosion and my phone doesnt have any. Cant I use this into my advantage?
Sorry, but the warranty on an iPhone is only valid in the country in which the iPhone is sold. So you can get an iPhone sold in Peru serviced only in Peru. And again, Movistar is the service provider for phones purchased from them, so it's them to whom you would have to appeal. You can try pointing them to the support page you mention, but they continue to refuse a warranty claim, there won't be anything you can do.