The Net::FTP module is only one component of a bundle or library of networking modules. You can't just install it by copying FTP.pm into a directory called Net/. It depends on some of the other components in the bundled library.

The message you got is telling you that it could not do a Net::FTP::A->new() call, so that's a good sign that Net/FTP/A.pm is missing.

There is a right way to install bundles of modules and a wrong way. The proper installation methods vary, depending on your platform and packaging preferences. Look for installation instructions with the bundle.