Galaxy S3 Can't Answer When Call On Hold

[TheDict8or]

I have a Galaxy S3, T-Mobile, 32 GB. They recently sent me update, and since then if I have a call on hold or hang up on a current call the second call won't answer. The icon goes out beyond the circle, but nothing happens. It seems that I can reject the call, however. Since I dispatch a small fleet my phone is pretty vital, and this is becoming a real pain. Any Ideas? Thanks!!