Strange Samsung Focus battery/charging problem - Please help!

[AllanUSC]

I've owned my Samsung Focus for about a year and a half with no problems, until this week.

A few days ago the phone started sounding off, as if I had plugged it in to be charged, even though it wasn't connected to anything. And the tone kept repeating continuously, sometimes more than once a second.

In this state the phone pretty much still works, if I can deal with the noise but the battery charging indicator keeps randomly flashing, like I'm plugging and unplugging it. The screen never shuts off and within a couple of hours the battery is almost completely drained.

If I plug the phone in to be charged, the sound stops, the phone works and charges normally.

My first thought was that there's a problem with the charging port. If I connect a data/charging cable that's not connected to the charger, the sound never stops. The only way to stop the sound is to charge the phone.

Luckily the volume still works and if I set the volume to zero, I hear nothing and can use the phone.

Has anyone ever had this problem? Is there a fix?

Thanks in advance.