@buddy : as a matter of interest, what APN are you using? I take it you have a datacard. Novatel or Option? Also, do you have/have access to a 3G phone, say a 6680 or 6630? Let me know and I will try and help you with some pointers on the technical side with well known bandwidth hoggers...
I am a prepaid customer on Voda for data, so I cant draw direct comparisons between my service and your service. But I will say this - I haven't encountered ANY billing discrepencies (and trust me when I say that I am @n@lly retentitive when it comes to things like this)! I have also not encountered any serious performance issues, other than the DNS resolving issues (which I "fixed" myself by installing my own local DNS server with a longer timeout), and the problems with the SMTP server (which I "Fixed" by installing a local SMTP service on my notebook, as an interim measure).