10-15 second delay before I can hear audio when placing calls????

I have had a strange problem that I haven't been able to figure out until recently.... When I place a phone call, the answering party will pickup and say hello (or when calling voicemail - the voicemail message will play) but I don't hear it.... At first I thought the calls were being dropped until I realized there was just a delay...

If the answering party says "hello" 2 or 3 times, I will finally hear them and the call can go on with no other problems. When dialing voicemail (*97) I don't hear the "please enter your password" message --- but if I simply enter the password after 5 or 6 seconds of waiting to hear something, it will drop me into the voicemail system...

So the problem I am having is this delay in receiving audio once a call is connected...

Is there any easy way to diagnose what is actually causing this problem???????

THANKS!