I tried these links to download java client form my cellphone.
http://gsm.voipbuster.com/download/voipbuster.jar
and
http://gsm.voipbuster.com/download/voipclient.jad
All ok on my N70 Nokia with my voipbuster, smslisto and calleasy account. (i think it works fine on any betamax service)
Really interesting to know also my credit balance and setup requested only few seconds to put in my account name, password and registered number.
Sms and some calls are now less expensive for me