Corrosion on charging port

[Semiclnbk]

Verizon is saying that my original phone returned because it was not holding a charge has corrosion damage inn the charging port. The water damage indicators were not triggered and for the life if me I know if no time my phone was exposed to any liquids ir even high humidity. From the time I first received phone it often got a slight catch in it when I hooked it up to charger. But I would carefully and just slightly wiggle it and it was okay. Is there any way that this problem or another problem could have caused the battery to overheat and leak causing the corrosion. It's driving me crazy because I am very sure that there was no water damage and they are charging me $299 for a water damaged phone. Coincidently the first replacement phone also failed to hold a charge from the time I received it and I'm concerned that they will charge me another $299 fee for that phone which wasn't ever working properly. I don't feel like this is fair but i don't know what to say or do about it. I get the impression from the phone rep and the in store sales person that I'm not the first or only person in this situation. I'd truly appreciate any help you can give me