If you are on their network, or using it, there is no means of blocking
where you go or visit.
Where you go, what you visit will be recorded in the logs, accessible to
their IT staff but is not public ally available information
To 'hide' or obscure where you go/what you visit from the logs you
perforce have to be off their network
I won't go into the details here its off topic but look for ssh/ssl
tunneling, vpn, etc.
tim