There were/are several versions of Hotspot, at least three. BTL blocked the 128kb service that cost just over US$100 a year. I had a little over 2 months use out of it for VoIP. The way that BTL's VoIP detecting software works it's clear that any standard VPN that becomes popular is then detected and blocked. Not wholly blocked, just degraded - good enough for text traffic but not for voice. They pick up those VPNs by traffic volumes & types, and by reading websites such as this. They devote a lot of resources to enforcing their (illegal) block.

What works best is a VPN service that's interactive, detects interference from BTL and responds to it. I have no intention of naming any of those here.

Actually, the free version of a VPN often makes a lot of sense initially, as BTL haven't yet had time to detect it. And using the free version of software in general where there's also a "full" paid version also sometimes makes sense, as it keeps the provider on their toes hoping you'll buy. Once you've paid you have absolutely no clout over them.