WE got around the constant harassment calling by simply stating WE would call them when WE delivered. I would as well refuse or ignore their incessant calling.
They would not keep calling me because I would not be civil with them after the third call in 5 hours (from p/u pt.) regarding "where are you and when do you expect to deliver". I would tell them ONCE (at p/u pt.) that I will deliver on or before the designated time unless Mechanical events or Natural occurrences prevent such delivery.
They don't like sarcasm yet sarcasm doesn't matter when they're being a pain in paying or settlement.
In comparison, most BROKErs don't like sarcasm yet most don't have a problem with it either because they deal with such a variety of Drivers.