I think the call blew up too quickly for it to be Kim. That would be out of line with what we know about their past relationship. The only way I can see Jimmy reacting that way with Kim is if she told him that the feds are putting the squeeze on her, as his ex-wife, and that by refusing to talk she has suffered consequences which she is fine with. Like he got angry when hearing from Francesca about the Feds finding the other sources of income. Maybe still technically married to him and had some assets seized?
My guess is that someone else came on the line and told Jimmy that Kim has left the company and they are not going to give him a forwarding number on her. And maybe, like someone else theorized, that the sprinkler company”s number is now a controlled line.
I don’t believe Francesca told Jimmy she works at a sprinkler company, did she? Only that she was asking about him? So he must have had some contact with her over the years?