Palm has just released a small update for the Treo 500v - in case you have a VodaFone UK SIM card in your 500v and do not get voicemail notification SMS; please head over to Palm’s web site and download a small .cab file that should fix the problem:
http://kb.palm.com/SRVS/CGI-BIN/WEBCGI.EXE/,/?St=2,E=0000000000901692981,K=1272,Sxi=17,Case=Obj(2233)