I have switched from VONAGE to Optimum voice, have purchased a $3000 phone system and calls still drop. Broad band is sufficient to handle the volume, so it is not a VOIP issue and was likely never a VONAGE service issue. After all this, the issue may be in a faulty phone line from the source to the wall jack by the reception area.
Of course everyone blames everyone else, but I am zeroing in on the problem. In the meantime, we just march on and continue to function.