1) This question has nothing to do with mIRC, as you state that you were using ICQ. The two are completely different programs, although they do have some similarities.
2) This proper section for this question is the Connection Issues area.
Regardless of the above, z-lines (or any other kind of ban/line) has nothing to do with mIRC, but rather the IRC network.
If you can't find the contact information for the network, relay the name of the network and we'll see what we can do about getting you the information you need to contact them.