If the problem happens on all calls and all phones, the issue might be with one of your calling features.
Call Waiting is an especially common feature that causes beeps during a call. When you receive another call, you will hear a beep that might cause you to miss a bit of the conversation. You are still connected to the original call and haven't been disconnected. You can read more about Call Waiting.
Call Forwarding is another feature that can cause seemingly unusual behavior on your phone. If your line has call forwarding activated, any incoming calls will ring once before they are forwarded. It's easy to turn off call forwarding — press *73 or 73#, depending on your location. This will allow calls to ring through to your line as normal. Read more about Call Forwarding.
After checking your equipment and your calling features, if you are still having problems, please contact us for more support.