I've used the mod Simgirl suggested in all my games from just SLS to basegame, nightlife and later as I added all EP's and SP's. It has worked wonderfully in all games. Tells you when to call your friends back along with a few other features. Thunder may have had a hidden conflict.
I think the your "call-at-work"(etc) suggestion would be a nice idea though. Even cooler if you had message options based on relationship, like:
"How about going out on the town tonight? Call me around___(insert off hours)"
or
"Have to run business meeting--can you call me back @ ___? <--Insert off hours for high relationship or for low relationship/enemy add "like never! thanks".
Or many be even too may calls affect the persons work performance ( or just have the message say it is); I second RedMist's idea/ request. (well part of it anyway

).