My wife started getting loud screeching sounds about a minute into calls made on her mobile. She has spent a total of about 5 hours talking to virgin mobile trying to resolve it. First she was told that it was a faulty mast. Then it was a faulty sim so they sent a new one. That didn't solve the problem so the assumption was made that it must be the phone so she ordered a different samsung phone on a new contract for more money. And that hasn't sorted the problem as it has started happening again. Surely it can only be the service provider as that's all that's left.. It has also started happening on my phone.