I can understand the hold time. There are certainly peaks and valleys in incoming calls. Our reps should be letting the rest of the people know when hold times get high to others can jump on. That happened earlier today and a few people not scheduled to be on the phones at that time logged in to reduce the hold times.
Did the ringing 20 times happen after being on hole? I don't think that's possible. After being on hold, when your call is transferred to a rep, it rings on their phone only 4 or 5 times. If they don't answer, your call is redirected into the holding queue.
The only time I could explain the phone ringing with no answer is if you dialed the main number and this happened. There is a certain number of lines we have that are using for incoming and outgoing calls. If all are busy, then you would just get ringing when calling in.