Have had serenata for a while and functioned flawlessly. Then experienced problem with outgoing microphone -sounded like it was on mute though could still be heard. Sent off to B & O under warranty. Received an estimate stating that they wanted 736 euros + tax to repair! as they had found evidence of liquid in the phone and this invalidates the warranty . Though phone is 2nd hand I've had no problems with it other than the mike problem. I can only think it's potentially a condesation problem . A term mentioned by B & O. 

Has anyone experienced a similar moisture related problem attibutable to condesation. Am hoping B & O will help me out. Appears the high cost is that they have to replace everything to re-honour the warranty. Hoping they'll just sort the mike. Not bothered about the warranty. They even wanted 27 euros to return the broken phone to me! Would "bite the bullet" if I'd done something to it but I haven't.

Most mobile phones have a water sensitive sticker in them that changes colour when exposed to water. I'm not sure if the Serenata has this.... but most phones do.

Could it be that it was at some stage exposed to water before you bought the phone? If so then I guess the warranty is void.

At that price they want to charge you for repair you could buy a new one on ebay or even from a dealer as they have some half price deals etc.