Vodacom is Blocking Sites with VPN

Vodacom's uncapped data service in Johannesburg is mostly reliable, but I work on many sites every day that do not allow VPNs. I have no VPN services connected to my computer, but in the last week, I am constantly being blocked from sites that accuse me of using a VPN. Google Captcha has also recently blocked me. When I change my connection away from Vodacom, all problems are resolved. What is Vodacom doing that's blocking my site connections?

It's important to me that this issue gets resolved as quickly as possible, failing which, I will need to find another service provider. I simply cannot afford to be blocked from these sites.