We have a corporate account and one of our users had casual data and decided he wanted a data plan so I added the 100MB bundle.
Before adding the bundle, he was getting speeds of around 400kbit.
After adding the bundle he complained that data was unusable, I've assumed it was coverage/his handset.
This morning we did some testing:
VF Speedtest was giving results of 100kbit (handset had 3G, not GPRS, unusable for VPN back to office though)
I called 888 and removed the data plan (back to casual data).
VF Speedtest went back up to 350-400kbit.
The handset being used is a Nokia 3710, which I believe is a plain UMTS (not HSDPA) hence not getting faster than that with the data plan removed.
How do I explain the speed difference though?