Unfortunately, not all popular VPN services provide anonymity.
VPN is, in a sense, a tunnel through which encrypted data is transmitted. Your ISP does not have the ability to see which sites you visit, what you type in, etc. Also, the site you are visiting receives not your real IP address, but the VPN server address. It would seem that there is nothing to worry about. In fact, it's not like that.
Currently, commercial providers offer the following VPN protocols:
PPTP is used most widely, fast, easy to configure, but is considered "least secure" compared to the rest.
L2TP + IPSec. L2TP provides “transportation”, and IPSec is responsible for encryption. This bundle has stronger encryption than PPTP. It does not have most vulnerabilities that PPTP has. It also provides message integrity and each party authentication.