djrob that totally sucks. Many realtors, including myself NEVER put the phone number for the client in the listing. Even with that said, when I have had listings expire or cancel, my clients tell me that they two are solicited pretty rigorously. Many of these bottom feeders use services to get your phone number. It sucks 100%.
Definitely call your agent or broker and have them get into the expired listing and put in big bold letters DO NOT SOLICIT CLIENT in the remarks field….It may help but since the listing is already expired, it probably will not. You want those comments put in the listing prior to expiration.
Also next listing do not have the agent put your number in the listing. That will help a little bit but not much. Just know, even if you did not have your number posted, it is very likely that these guys would have found it, and you still would be getting solicited. I have had people tell me that agents even came to the house.